Gliding
Sheesh
I notice you're based in London, and would point out that some the rates being quoted by our Murcan friends are a little on the light side. Expect to pay somewhere between £200 and £400 for membership of UK clubs, £5-£8 for a winch launch, 25p-50p per minute glider rental, and typically £25 to 2000 feet aerotow. You'll find the big clubs near London are at the top end of cost scale, but do have good fleets and facilities.
I struggled in the early stages of my gliding career - never a natural, but now enjoy the luxury of having my own glider and being able to b*gger off for 3-6 hours at a time on the good cross country days, family permitting. Long cross-countries are completely absorbing and a great challenge. Check out the clickable map at gliding.co.uk for directions to websites of most UK clubs.
I've just never been able to understand why the gliding fraternity usually requires an instructor rating to fly passengers, so you have the odd situation where a 45 hour PPL can take pax whereas a 500 hour non-instructor in gliding cannot. I had to take a BGA Basic Instructor rating to be granted the privilege of flying my kids and friends, but worth the effort and expense, particularly as it ironed out 10 years' worth of ingrained bad habits from solo flying !
Regards
Pegpilot