Had to remove the panel across the back and the side panel on the LHS and the horizontal one near the back LHS window, not completely, just enough to access by hand and drill a new hole from the top for Engel socket.
Whole job took around 5 hours easy, getting the main cable under the B pillar and then down through the back cross member was probably the most difficult. Like everything it would take a lot less time if done again.
Removing the spare wheel does help a lot.
Cheers