Had the same problem with mine, destroyed donuts in 300 miles so deceided to get shut of it. Mines lifted and I think it causes premature failure.
Need a 200tdi prop, they shuldn't have donuts, so if yur mates has its a bit of an odd one.
To get the yolk off the diff you need to heat it up to break the sealant down and wind in an M8 bolt i think to jack the centre out. You can then see the nut holding the flange.
The 4 bolt flange and spacer from a 200tdi / RR classic rear axle diff input will be needed along with the SPACER (bit awkward to get out as it sits below the oil seal) behind it. You will need to reuse the nut from the 300 diff as the threads are different of the 2 diffs.
If yu need anymore info just PM me.