First post so apologies if I get anything wrong (posting from a mobile so I can't add a picture).
Just been on the phone to O2 to attempt to upgrade to the HTC HD2 but as my contract doesn't run out until January I couldn't. However, the bloke in the phone said I could buy the phone outright for £277.72. Given the fact that other retailers are offering this for £500+, it seemed a bargain to me!
Not sure if it's unlocked but O2 phones often are. I've ordered one so will let you know once mine arrives. Either way, if you were going to put a O2 sim in it's a steal at over £220 less than play.com.
Edit: This deal does not appear on their website, you need to call customer services. The number is 202 from an O2 handset.