I'm coming to London in November (not sure when yet though, I want to go sooner, but I also want to wait until the end of November to catch the Chelsea-Arsenal match if it's not really expensive and impossible to get tickets too, though it probably is) and I'm wondering about using my iPhone there. I'm from the US for the record. Is there an O2 near Heathrow? Whether there is or not, would I be able to and would it be feasible to get a SIM card there and do pay as you go? Any info would be greatly appreciated.