I've made progress!!
But it's two steps forward and one back..
On the off-side rear, about 6 inches behind the rear light, is where the cable loom passes through the bulkhead. above this point is another grommet / pass-through area that's not used, so I used that. Hey presto!! If i stuff my hand into the area inside the engine bay, i get a dirty hand... But I can feel the end of the cable poking through.
I've coiled the cable in the void underneath the rear quarter speaker as now I'm stuck... the plastic sill section that contains the boot/bonnet switches..How do i remove it? There are two plugs, I removed those, but I can't figure what I need to undo? I shoved all sorts of implements into the holes without any success (where have I heard that before...)
i'm going to google it though.. But just in case someone knows here, let me know
Next steps:
Get the cable run up to the head unit, under the sill
Get the bumper off
Drill a hole in the bumper (eeek)
splice off the power from the reverse bulb feed. Two wires are needed here - one to power the camera and the other to provide a signal to the H/U to tell it it's in reverse.
put it all back together!!
so yeah, a little way to go!