I had an initial attempt at swapping them but couldn't figure out exactly how to prize the cover off. I didn't want to damage any parts so after some searching found a site where I could get a full workshop manual for the C7 (well worth a tenner!). If anyone wants a link to this site drop me a PM. To replace the cover you need a small suction cup to take the mirror itself out the housing. Remove the two screws at the back and basically then pull forcefully the cover forward and upwards to pull it out of its housing with the bottom camera holder and plastic attached. Swap the camera plastic housing over to the new cover with two screws. The PITA bit is getting it back on which takes a fair bit of fiddling and snapping the bits back into place until you get a good fit. Anyway here is the end result. I chose to swap the centre caps on the wheels for black ones while I was at it.
