vj, there are 3 large clubs near London that will provide courses which would suit your requirements. Lasham, Booker (at Wycombe Air Park) or the London Gliding Club at Dunstable.
Book on a course, and after that decide how involved you want to get. But if you can afford to live in London, you can afford to fly at these 3 big clubs, which have professional staff.
I started flying in 1983, at Booker. Went solo in 3 months, got Silver Certificate the following summer, and did the PPL at Wycombe Air Centre that winter, only needed 18 hours of power as the Silver C fills a lot of the requirements.
The British Gliding Association site is worth looking at. The Glider Pilot forum is not very helpful, not as user friendly as PPRuNe, so hard to follow, and a bit inbred. Ask your questions on this forum and we'll do our best to help.