I've been looking into this myself a lot =)
One program I LOVE is Swagbucks (see my signature). My husband and I normally earn $25 each/month (redeemed as Amazon.com gift cards) using Swagbucks. We do put some effort into it to get that much, but even with minimal effort I easily earn enough Swagbucks to get $10 worth of Amazon.com gift cards/month. How it works is you use their search engine, you can do surveys, play games, watch videos, etc. and you earn Swagbucks (like points basically), and then you can redeem those points for prizes.
I don't really know what other programs are available for the UK. I know Swagbucks has a UK program, so like instead of Amazon.com gift cards you can get Amazon.co.uk cards. At least in the U.S. I can also cash in my points for paypal money, which I could then transfer to our bank account, but the Amazon cards cost less Swagbucks/dollar. Granted, it's not a lot of money, but you could put it towards a few grocery items, or gifts for weddings/birthdays/Christmas, etc. to free up some more money in your bank account.
I'm not sure what else you could do. I know Amazon also has a program called mturk, where you do menial little tasks for little pay usually, but sometimes I do that and it slowly adds up. I usually then add that to my Amazon.com account to boost my balance there, but you can add it directly to your bank account... At least in the U.S.! Sorry I guess I'm not much help since I don't know what's available there.