e2save have brought back the Virgin "SIM ONLY" contract with 6 months free line rental on a 6 month contract (after cashback) after which you can cancel. You get 150 any time, any network minutes and 150 text messages per month.
This is great if you don't want a new phone, don't want a long contract because you're waiting for a new phone to come out or otherwise. The important thing is that you phone must either be UNLOCKED to any network or locked to Virgin... either will do.
You initially pay £15 per month to Virgin Mobile. The deal works by cashback which you claim from e2save at months 3 and 6 (a total of £90 over 6 months). I suggest that you send these via recorded delivery. You have 30 days from the date on the bill to send your claim: plenty of time!! The whole thing then works out as totally free... and you've just gotten yourself 900 free mins and 900 free texts out of the bargain. If you wish, you can also purchase via QuidCo.com for £7.50 in extra cashback.