Hi Carl, i used to have have a 2.0d x type and I had the same problem for a while, it is a common problem I believe, anyway it was the two small arms on the rear suspension, if you look under the car from the rear you will see two suspension arms on each side, they go from the rear wheels and go up at an angle, not a great description, but you will see them, I took them off and greased them up, refitted them and hey presto..noise gone! hope this helps. ;-)