In reply to count: As others have said, 50m double ropes in the range 8.3-8.6mm are generally considered the best 'all round' option for UK trad rock climbing.
Any of Beal Cobra, Mammut Genesis or DMM Prophet will give you good service.
Things are no longer as simple as they once were as single ropes are now available down to 8.7mm and 60m or even 70m ropes are increasing common. However, the routes most people climb haven't changed, so I'd strongly recommend sticking with fairly standard option of 50m doubles around 8.5mm unless you have a very particular reason not to.