Don't overlook Oxford Gliding Club - a friendly weekend only civillian club which operates from RAF Weston on the Green. I came here 22 + years ago and been here ever since, although as Chairman now I will admit to a slight bias!
I've just got myself an NPPL SSEA from PFT at Kidlington (a great bunch I'd highly recommend by the way!) and converting from a Glider Pilots Licence I only needed to do a minimum of 10 hrs - a significant cost saving plus the best basic training you will ever get.
PM me if you want to give us a try.