As there aren't many 12 month free on a 12 month contract I thought I'd post this. It is with buymobilephones.net who seem to be quite reliable with cashback and free gifts. Deal is for 300 mins and 200 texts and will cost £30 pm - all of which will be refunded as long as you follow the fairly simple redemption rules!
As with all cashback deals you need to be organised, so if you aren't this isn't the deal for you. And also make sure you send letters by special delivery with consequential loss cover. Ducky has a great cashback guide.
I know some people don't like redemption deals, but I, and thousands of others on here, have done them for years without any problems.
Also quidco is £20, which should just about cover your postage making the deal totally free over 12 months if you don't go over the line rental limits.