Bit of a late response, but I've just joined the forum.
I placed my dashcam to the left of the Sensus module, ran the cable along the roof liner, inside the front of the A pillar (DO NOT cross the A pillar as it could affect airbag deployment) and down below the glove compartment to the fusebox. I used fuse 58 as that is used for a TV in some models, but I don't have a TV so it's all good. The ground point is a fixing bolt that sits just at the front of the fuse box as you look at it.
Problem for me is the rear optional camera doesn't have a long enough cable to connect to the main unit!!
