OK so Santa bought me a Nextbase 312GW which while I await my hardwire kit is connected to the rear passenger 12v socket in the centre console. This seems a good option. I can easily hide the wiring under the roof lining and tuck it behind the the rubber trim on the door pillars.

I originally took it to the power socket in the boot but thats permanent & I didn't want to have to keep turning the camera on and off or risk draining the battery.
Can anyone suggest a fuse to piggyback off? I'll use the fuses under the glovebox. It seems box A fuse 22 which is the centre console 12v sockets.