I signed up to go4it.freebiejeebies.co.uk about a year ago. Since then, I have received countless high value items, and I have only ever spent the inital £5 on completing one of the listed offers to qualify. Gala Bingo and Coral are the ones that cost a one off £5, however IF YOU DON'T WANT TO SPEND ANYTHING on completing your offer, there is a Lovefilm free trial offer. This is great because you receive free DVD rentals in the post during the free trial, it just takes a bit longer to credit to your account than Gala and Coral.
BBC approved this system a while back, it's not to be missed and there is nothing to lose by trying.