So it's late in the game (meaning I don't have much time to research, buy, ship, etc), but I've concluded that I don't want to pay Cingular (my US carrier) a dollar a minute to use my phone in the UK. It is not unlocked and it can't be unlocked. So... any recommendations for having a cellphone in London? Specifically, renting for a week, vs. buying one in the US and buying a pre-paid UK sim. Anybody have recent experience with either of these methods?