Just found it on three. Nokia 5800 refurbished on 24 month contract, 300 mix and match minutes, 500 mb data: All that for £10 a month. Also, you get unlimited skype to skype calls, free three to three calls live msn messenger etc.
Possible £32 quido and Refer a friend. Plus you may get £20 accessory voucher when you buy online.
Or you can have a refurbished Nokia E71 for an extra quid. There are other phones too. Look here: http://threestore.three.co.uk/refurb.aspx