Please, Please don't buy from the carphone warehouse (whorehouse as I've heard it said) - I did because I wanted to pre-order and O2 had just sold out of 16GBs... and now regret it! I wanted to get mine replaced, the idiot refused to see that there was a problem, ran the IMEI number through the system and told me that the phone was not the one that I had been sold...
That morning I had phoned up to check stock levels, was told they had loads, phoned again just before I was due to leave (after having cancelled all my afternoon appointments), and was told they had none in stock - after a lot of complaining, they eventually told me that they were all reserved (which they are NOT allowed to do!).
Just go to an Apple store - the people who work there actually know what they are talking about. The genius I dealt with after going to the CPW had an iPhone that had the same problem as mine (even worse actually; yellow screen) and just asked me what I wanted him to do, I said "Please replace it anyway" and he did just that.
Sorry to take it off topic - but I would strongly advise anyone against buying from the whorehouse. When I phoned up to ask about replacement options, they offered for me to send it off to be checked. I asked if they would send a replacement first with a deposit and the woman could not understand that I need to keep a phone to use and can't just send it away!