My mate did the unthinkable a few days ago, and dropped my iPhone 4, shattering the glass on the back, had it been the front, I'd have shattered him! As chance would have it, I cancelled my insurance policy for my iPhone with O2 about a month and a half ago... I've read around a bit, and it looks like replacing the back by myself would be simple, but I'm worried about buying a part which is not an official Apple part, and of course the fact that doing so would void my warranty. How much would Apple charge for a repair (I'm in the UK) of the back glass, assuming they can do with without having to charge me for a whole replacement iPhone? Thanks.