Rear Diff/Drive Shaft Knocks.

I have a knock from rear. Did the obvious and changed the rear diff nose bush for a polyurethane one, knock still there.
Only happens when going round sharp corner left or right, with or without power applied, I seem to get three(a small number anyway) knocks in rapid succession which I think are speed dependant, sounds like the noise is coming from the middle rear, rather than one corner.
Will happily go full lock left and right at tickover, forward and reverse with no noises and no perceivable drag.
Grabbing the rear drive shafts there is slight axial movement, I believe there should be, and barely perceivable radial movement.
VCU is not seized, haven't done the timed one wheel up test, but with one wheel up and the wheel brace I can slowly turn the wheel and watch the back half of the prop shaft turn.
Car is a 2002 TD4 with 200,000 miles.
Any pointers, ideas gratefully received!

Thanks,

Chris.

At 200K miles the noise could be from a multitude of items.

The VCU is well past the average failure distance for a start.

The rear diff could be starting to wear. Has it's oil been changed in all those miles?

The rear CV joints could potentially cause clicking noises.

The UJs on the propshafts will also be past there best and can cause clicking under load.

The rear subframe could be breaking loose from the chassis rails. That was a known fault for some years of FL1 and will cause clicking, although the sound originates from one side or the other.

Lots of investigation I'm afraid.

Thanks for the prompt suggestions.
Tis on second VCU, changed on spec at about 100k after reading all the suggestions on here, so yes, possibly due replacement but I do keep an eye on it!
Had the car from new, clutch has just started to slip too, so have to think about repair bill versus replacement!

Chris