Round the London orbital are the following airfields which have PPL schools:
Stapleford
Biggin Hill
Redhill
Fairoaks
Blackbushe
White Waltham
Booker (Wycombe Air Park)
Denham
Elstree
Don't think I've missed any out? All have their pros and cons. Recommend you take a trial lesson at a couple before you commit yourself.
Regards
jez