As far as I can tell this part is not removable.
I wanted to replace mine in the TDI75, as the brass inserts and lugs that hold the battery clamp in place,
have sheared off at some point in the cars life. (shame as its got he rare spare wheel mount battery clamp)
Ive exampined both my TDI and the Donor car ive been stealing the twist interior bits from, but its looks
to be bonded to the aluminum body in some way or may be an interference fit.
Ive also experienced water in the boot/battery area and wet rear seats, finally replaced and resealed
rear vents and OSS and car is now bone dry, carpet replaced etc etc.
There was a good few inches of silicone applied around the outside of the old rear bumper
vents when removed, so will assume this was a recurring issue !