Bristol GS is one of the best IMHO. Whilst I didn't use them, my hubby did and he has nothing but praise for them. (He's ex Ansett now with easyJet)
I haven't flown with Oxford and while they have a reasonable reputation, there are other very good flight schools out there that don't demand you do their theory course. I would ask them who they think you should have a look at.
Go and visit as many schools as you can find. Get a "feel" for them, what may fit you may not necessarily fit another.