Statement Of Financial Position [Abstract]
| Concept | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2021-12-31 | As at 2021-12-31 | As at 2021-12-31 | As at 2021-12-31 | As at 2021-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||
| Assets [abstract] | |||||||||||||||
| Non-current assets [abstract] | |||||||||||||||
| Property, plant and equipment | — | — | — | 
                                                11,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                13,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Trade and other non-current receivables | — | — | — | 
                                                12,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                6,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | 
                                                3,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                3,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | 
                                                52,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                48,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current assets [abstract] | |||||||||||||||
| Current inventories | — | — | — | 
                                                500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Trade and other current receivables | — | — | — | 
                                                52,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                55,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current tax assets, current | — | — | — | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Cash and cash equivalents | — | — | — | 
                                                29,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                22,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | 
                                                20,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current assets | — | — | — | 
                                                167,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                132,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | 
                                                219,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                181,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Equity and liabilities [abstract] | |||||||||||||||
| Equity [abstract] | |||||||||||||||
| Issued capital | — | — | — | 
                                                5,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                4,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | 
                                                34,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                29,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Share premium | — | — | — | 
                                                13,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                4,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Equity | 
                                                13,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                5,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                34,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                53,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                38,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                4,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                29,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                4,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                26,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                17,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                4,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                4,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Liabilities [abstract] | |||||||||||||||
| Non-current liabilities [abstract] | |||||||||||||||
| Trade and other non-current payables | — | — | — | 
                                                3,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                2,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Non-current liabilities | — | — | — | 
                                                20,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                21,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current liabilities [abstract] | |||||||||||||||
| Trade and other current payables | — | — | — | 
                                                126,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                96,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | 
                                                145,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                121,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | 
                                                166,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
                                                142,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |