Remove outer surround from lock on door card, remove door card (held in place with clips)
There are four fixings to the outer cover, there is a hole in the metal panel, nearest hinge to engage to spline fixing at an angle, using a small extension.
I removed the others followings removing two nuts (13mm) holding metal plate (lock mechanism) and two spline fixings. I managed to get to the others with the lock mechanism plate loose
I fitted my camera as near centre as possible, had to make my own bracket out of stainless steel. I pulled a wiring through for the number plate lights and added another grommet, which would cope with the extra cables, so didn't drill another hole.
This is not easy, please can someone post pics showing how to remove the locking mechanism from the door as I have tried this to locate hole for wiring for a reverse camera and it's proving very difficult