VGS at Kenley - free (you probably even get expenses)
ULAS - not SE London, but you do get paid to go flying. You do not need to join the RAF afterwards.
Flying scholarships - ATC, Air League, GAPAN etc all give free flying.
If you are determined to pay for your own flying, then why not consider something more realistic (like gliding/paragliding, microlighting) which you can continue until you have enough money to pay for SEP flying. Whichever for of aviation you chose it will never be cheap.
Good luck
