Welcome back, 1470!
Funny thing, we were just having a meeting about you last weekend! Or how to bring back all those talented people who had discovered flying in the Air Cadets....
First of all, the British Gliding Association website has several links to finding your local clubs. Yes, Sutton Bank is one, York another, and there may be others. I presume you have a job that keeps you in that neighbourhood.
I strongly recommend you visit in person two or three of your nearest clubs and see which one suits you....where the welcome is warmest, where you feel you will fit in, talk to people, ask about the training. Most certainly your experience should help you to progress very quickly.
Instructors cost nothing. At my club, in middle earth, if you are a club member (students get special rates, ask for that!) a winch launch costs £7, an airtow £28 to 2,000'. A K-13 glider is 25 p a minute. Single seaters not much more, sometimes even less!
Recommend that you fly the club single seaters first, then contemplate if finance allows, joining a syndicate. There are certain requirements for flying friends and family, and one must complete a course before becoming an instructor. Sometimes a club will help with this financially, if you are committed to help out the club!
But the MOST fun is cross country flying! (If you get it wrong, you visit a farmer!) Flying in wave. Rock polishing in mountain areas. And eventually, competitions. In gliding, we help each other, which keeps costs down. Club members should help get the kit out in the morning, or help put it away in the evening when flying is done. And then we open the bar!