Statement Of Financial Position [Abstract]
| Concept | As at 2024-12-28 | As at 2024-12-28 | As at 2024-12-28 | As at 2024-12-28 | As at 2023-12-30 | As at 2023-12-30 | As at 2023-12-30 | As at 2023-12-30 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | ||||||||||||
| Assets [abstract] | ||||||||||||
| Non-current assets [abstract] | ||||||||||||
| Property, plant and equipment | — | 
                                                900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Right-of-use assets | — | 
                                                700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Goodwill | — | 
                                                13,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                13,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Intangible assets other than goodwill | — | 
                                                12,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                11,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Deferred tax assets | — | 
                                                1,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Non-current assets | — | 
                                                29,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                30,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current assets [abstract] | ||||||||||||
| Current inventories | — | 
                                                100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Trade and other current receivables | — | 
                                                19,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                15,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Cash and cash equivalents | — | 
                                                10,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                10,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                27,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | 
| Current assets | — | 
                                                30,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                26,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Assets | — | 
                                                60,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                57,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Equity and liabilities [abstract] | ||||||||||||
| Equity [abstract] | ||||||||||||
| Issued capital | — | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Retained earnings | — | 
                                                9,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Share premium | — | 
                                                27,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                27,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Equity | 
                                                9,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                37,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                27,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                7,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                27,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                35,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                34,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                24,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                9,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Liabilities [abstract] | ||||||||||||
| Non-current liabilities [abstract] | ||||||||||||
| Non-current liabilities | — | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current liabilities [abstract] | ||||||||||||
| Current provisions [abstract] | ||||||||||||
| Current provisions | — | 
                                                600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Trade and other current payables | — | 
                                                21,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                19,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current liabilities other than liabilities included in disposal groups classified as held for sale | — | 
                                                -
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current liabilities | — | 
                                                22,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                21,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Liabilities | — | 
                                                22,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                21,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — |