Found a WestFalia installation guide for a tow bar to a bmax, and looking at it, you have to dismantle parts behind the rear bumper. I am not sure if that is only for Westfalia specific tow bars or not though..... other tow bars may be more suited and less involved to attach.
If anyone is looking for a new towbar - I bought this one on ebay and can highly recommend it as it has the detachable tow-bar which allows the reversing collision detection to continue to work (when tow-bar removed and put in the boot).
Very good quality and fit - and looks like good engineering quality and included all electrics, socket and instructions. Plus it was an extremely good price!!!