T-Mobile has this micro SIM, suitable for an iPhone 4 or iPad, for £5 up front. A monthly top-up of £10 gets you 100 minutes, but the real draw is 12 months of free internet, worth £40.
The SIM must be purchased with £10 of credit.
With no text allowance, realistically this’ll appeal primarily to iPad users looking for a data SIM. T-Mobile’s Fair Usage Policy is 500MB per month.
Free delivery for online orders with T-Mobile.
(Thanks to grumbler on HUKD)