DON`T join the BGA unless you particularly want to, your club is all the connection you need to the BGA.
The BGA Magazine is Sailplane and Gliding, always referred to as S & G, and is available on subscription to the BGA, on order from your local newsagents or, at most clubs, on order through the club. In the latter case you get it a few days later than direct from the BGA but the club gets a cut.
By the way El Desperado, I believe you are an imposter. No one with the experience you claim could possibly admit that we madmen who fly without visible means of support, could know anything that you don`t already know, in spades.
Welcome to the best form of flying there is. Juat be prepared to spend a LOT of time on a windy airfield without actually doing any flying. It gets better once you are able to soar fairly reliably and have a share in your own aircraft. It doesn`t have to be a `Hot Ship`. There`s plenty of fun to be had with last years model or, as in my case, one from just over halfway through the last century.
Regards
Mike W