Since the Mobiles.co.uk deal I had ordered from went out of stock I started looking for deals myself, and found this.
Nokia 5800 (RED)
T-Mobile Combi 30 + Web and Walk = 300mins, 200txts, Unlimited Web (1gb FUP).
You get 6 months free via redemption on a nice short 12 Month Contract, and £20 cashback through Quidco.
So the total cost is £195.50 for the year, which works out at £16.30 a month.
To save any confusion here is some details about the fair use policy taken from the T-Mobile site. I think 1gb will be plenty for browsing etc, and I'll save my downloads for the home PC.
This plan comes with a fair use policy of 1GB a month. We'll monitor how much you send and receive each calendar month so that we can protect our network for all our web'n'walk customers. If you use more than your fair use policy amount, we won't charge you any more, but we may restrict how you can use your plan, depending on how often you go over your amount and by how much.