For anyone else wishing to do this - If you have a comand fitted, this is fairly straight forward.
I got myself a replacement boot handle with intregated camera kit (£20) and a Fakra adaptor cable to plumb it into the comand unit.
The estate is tricky as you need to dismantle the paneling in the tailgate to get to the handle, then run the cables through the rubber tube into the headlining and to the rear fusebox for power.
The video feed cable then needs to be routed to the front of the car and into the back of the comand unit which then needs to be setup for a reverse camera in the engineering menu.
Took me a few hours to complete and cost £30 all in. Very happy with the results.
Plenty of guides online - i've attached this one that I used as a reference, obviously the estate will take a different path to route the cables.