So if anyone is fitting one of these in the future this is how to remove and refit the rear mount into the MR kit.
This is the rear mount removed (i'm holding it upside down to what it would be fitted to the vehicle). There is a large threaded lug nut that is undone from the thread shown. This is accessed through the bottom of the cross member. You will need a 12mm hex head or T-60 trox bit to remove it.
The stud in the centre is pressed in as shown.
Place the non-threaded end of the stud over a large socket and with a brass hammer give it a couple of good belts and it will separate. Be careful not to damage the thread.
The stud head will need to be pressed in again before re-assembling into the new MR part. Do this by placing a long socket over the thread with the head of the stud on a vice or anvil and give a few solid belts to re-seat it. The second pic shows it reseated.
Now re-assemble the bush in the same order in the new MR part and using the long socket again press it back together with a couple of good taps with the hammer
Part is now ready to be installed.