I gather this probably isn't relevant in your case but with the iPod leads that connect into the head unit (mine was in the glovebox), the cable won't charge newer iPods/iPhones. Apple changed the charging pins in the connection (to do with the USB/FireWire hardware they're now using).
Good news is though that you can buy an adapter which is about the size of matchbox (perhaps a bit smaller) that you plug into the end of the cable and then into the iPod/iPhone, and it will work exactly as it should an charge too.
I'm sitting in Aylesbury Perrys waiting room at the moment so can't look it up but I bought mine from the Apple store for around a tenner if memory serves correctly. I still have mine somewhere if anybody wants it..