mine is battered and needs a new back. Anyone done this?

there's an app for that

My sister got hers refurbished after dropping it and cracking the back. Came back all shiny & new looking. Almost a different iPhone. OK, it probably was a different iPhone. A few days later her baby boy ran the screen over the tiles on the kitchen floor. Oh dear.

was that arranged through an Apple store? I've looked on t'interweb but can't find anything

Lad at work has had his replaced twice (for refurb'd units) just book an appointment with a specialist @ your local Apple store