Some gliding sites are winch only, some aerotow only and quite a lot do both. The logistics of flying round the country from site to site are complicated, needing weather and a retrieve crew for when the weather doesnt co-operate :-)
but its in theory quite possible, It was tried 2 years ago in a k21 but ended up trailering round mostly as the weather fir the period it was booked for was dire (search "glide britain"for lots of videos made at clubs they visited)
to fly away from the club you join you will need to have a bronze badge and cross country endorsement, neither hard to achieve if you stick at it.
Cross country flying is a truly exhilarating, challenging sport and im sure you will love it
good luck!