Disclosure Of Non-Current Assets Held For Sale And Discontinued Operations [Text Block]
| Concept | 2023-12-31 to 2024-12-28 | 2023-12-31 to 2024-12-28 | 2023-12-31 to 2024-12-28 | 2023-01-01 to 2023-12-30 | 2023-01-01 to 2023-12-30 | 2023-01-01 to 2023-12-30 | 
|---|---|---|---|---|---|---|
| Disclosure of non-current assets held for sale and discontinued operations [text block] | — | — | — | — | — | — | 
| Disclosure of analysis of single amount of discontinued operations [text block] | — | — | — | — | — | — | 
| Disclosure of analysis of single amount of discontinued operations [abstract] | ||||||
| Disclosure of analysis of single amount of discontinued operations [line items] | ||||||
| Profit (loss) before tax | 
                                                203,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                14,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                189,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                20,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                167 .7
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                188,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Revenue | 
                                                2,014,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                2, 014.4
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                1,809,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                1,809,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Cash flows from continuing and discontinued operations [abstract] | ||||||
| Cash flows from (used in) operating activities [abstract] | ||||||
| Cash flows from (used in) operating activities | 
                                                310,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
                                                3 10.8
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Cash flows from (used in) investing activities [abstract] | ||||||
| Cash flows from (used in) investing activities | 
                                                217 .1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
                                                191,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Cash flows from (used in) financing activities [abstract] | ||||||
| Cash flows from (used in) financing activities | 
                                                163,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
                                                115,900,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             |