Sorry to bring up an old post! About to install the same reverse camera. Did you remove the bumper and cut away the plastic bumper bracket that covers the whole in the bumper between the two number plate lights?
I did for mine back in July 21-
But 1.5 years later it is still not hooked it it up! 
I need to remove my sub enclosure, that is a complete pita to do! - and wire into the loom, need to find that how to thread on here that identifies the reverse wire.
Ah shame, was going to ask how it was! So you had the bumper off, cut off the plastic bumper bracket, then fed the cable though the grommet into the boot?
Have found a few useful videos on the wiring once in the car, just trying to figure out the easiest/best way to get the cables into the boot!
So glad I found this thread though, was going to get one that replaces the number plate light but this is a much better idea, and never knew there was already a hole between the number plate lights!
Cheers! Will
