So got my arse into gear thanks to this thread, hitch is on, needs finishing... who said an hour?
Some inspiration from this thread by Gaz,(
https://zroadster.org/articles/bmw-z3-rear-bumper-removal-procedure.56/ ) to take off the bumper. However I went a different way and left the wheels on along with the plastic supports in the wheel well. Nightmare to remove the bumper, but I took the rear lamps out then it was a breeze... sort of.
The Curt hitch uses the bumper brackets, and the cross member.
This is mine:
Below is an internet pic, someone else's car showing the cross member drilled and bolted.
The Curt instructions make it seem easy... yeah, they don't mention the stabilizer bar which takes some maneuvering around.
As Gaz mentioned the 4 plastic clips, grommets at the sides are toast. They may have been useful during assembly, but after 16 years they broke when trying to shift the bumper. Trip planned to BMW tomorrow for 4 replacements, if they have stock I will re-assemble.
Oh yes, I forgot. Don't drop the hitch on your nose, it f@@@ing hurts
Edit: added bumper removal link