Some gliding clubs within the UK have various schemes. You buy a membership and a scheme, you pay X amount of money (prices differ from club to club), and thats it you work through your scheme and then you top up... job done.
, however there is a slight draw back, I know from experience with flying K13, K21, K7s ect that your only up about 7 or 8 mins, which is great... just what you need. I learned a lot from "up round & down flights.
however you could find yourself towards the end of the year with too many hours left on your scheme and not enough time to get the scheme finished, thus you could end up loosing money
Afterwards why don't you consider getting a taildraggers licence, and go tugging. (just an idea for you to think about)
I sincerely hope this helps you and wish the very best of luck in flying gliders.
Regards SPMCUK