I'm told it could be the rear diff bush or low diff fluid, but having done a bit of searching im panicing now as this seems quite a common noise/problem, and usually ends up with an expensive new rear diff due to some play between the gears & pinions in the diff itself

http://forums.audiworld.com/tags.php?tag=clunking
Anyone else get this noise, is this a known fault?
Thanks again,
goose