iPhone, iPhone, iPhone.
..but not if the 'phone calls' function is an important feature for you.

If your current contract is with Orange, speak to them about your 'intended change of provider'.
I got a free HTC Desire with 600 mins (x-net and landlines), unlimited texts and e-mails, and 500mb internet allowance for £17.50 a month.
I've been with Orange for over ten years so 300 of the 600 mins allowance is some kind of 'loyalty bonus'.
The likes of Carphone Warehouse couldn't get anywhere near the 'Direct from Orange' deal. They said for £17.50 a month with the same mins etc they would have to charge me £299 for the phone.
Could have had the Desire HD for £2.50 more a month, but with a 4.3" screen (as 'fab' as that may be) I reckon it would be just that little bit too big for having with me pretty much every time I left the house.
The standard Desire has a 3.7" screen and that's plenty big e'nuff.