Well my Roadster is all sorted now. I changed the diff oil to the Red Line 75W90 that was recommended - the black and grey oil/sludge that came out showed me it was well overdue (probably the original factory diff oil from 2018!). Greased all the propshaft grease points. And while I was at it I've replaced the standard coil overs on the factory fit rear multi link suspension with the SSL dual rate ones (already has the SSL set-up on the front) - what a difference, she corners like she's on rails!
The diff clicking has stopped, however there is a little play in the diff, turning a wheel by hand and holding the prop shaft - is that normal?
I would like to thank everyone who commented on this thread it certainly steered me towards the remedies.
