Have you ever considered joining an ATC Volunteer Gliding School? Many all over the UK are looking for instructors (I'm thinking motorglider - Vigilant - here) and you get loads of hours, get to instruct and do a rewarding task for the good of youth/aviation - and you don't pay for your flying. However, you will have to put in a significant commitment - generally at least 3 full days (sat or sun) per month, but it is worth it. I average about 80hrs a year, and many people average a lot more.
Regards,
Blagger