Phones4U have got a variety of deals on the Sony Ericsson W995 on Vodafone, O2 and Orange at the moment. The pick of the bunch seems to be the Vodafone one.
You get free handset, 600 xnet mins, 3000 texts and unlimited internet plus £50 automatic cashback (no redemption required) and £35 Quidco for £30 a month on an 18 month contract.
The phone is excellently reviewed by most sources and is available for £199.95 on PAYG (£10 top up required). http://www.hotukdeals.com/item/508211/sony-ericsson-w995-vodafone-orange-?