Hi
Had a Detachable Westfalia on an A1 with simple electrics just wired into the loom with interface relay, no issues.
Current car is Q2 I ordered a Westfalia but was actually supplied with a Tow-Trust removeable bar as Westfalia was on extended delivery at that time. Had dedicated wiring loom and programming this time. All done by a local independant who did the work at home, all in for £425.
No issues towing an old school trailer with bulbs in which case the car detects the trailer and I get dashboard indication of turns. When I use a towbar mounted bike rack with LED lights, the current draw is too low so the car does not detect that anything is attached.
The Q2 did not require any bumper cut, already a hole in the right place for the bar and socket.
I now prefer the Tow-Trust bar and would order this type again in preference to the Westfalia. Attaching and removal seems easier and the lock and key is superior.