You could try the Pilot Centre at Denham, trains stop at Denham from the centre of london and Central line tube goes to Ruislip and change to train there. They will pick you up if you you give them a ring. 01895-833838, it's a nice friendly club with a good fleet of a/c ranging from C152/172/PA28 and a Citrabia for aero's...
Best of luck
Brgds
VP8