I’ve ended up with a voucher for 2 months free DVD rental from Lovefilm.com. Afaik you have to enter your credit card details, but they won’t start charging until the two months are up. I used them for quite a while and they seemed pretty good. The offer’s for their 2-DVDs-at-a-time £12.99 service, or the £16.99 two-DVDs-or-games package. Comment / email me if you want the code – I’ll update this post if it goes.
(I hope Lovefilm don’t mind this)