Hi Lee. My knocking issue turned out to be the exhaust hitting the rear drop link (whatever that is!). Maybe worth checking if you're still no closer to finding your cause?
UPDATE - just driven home and he has seemingly fixed it. He noticed that a part of the exhaust was knocking on something underneath the rear of the car and so he moved the brackets holding the exhaust slightly. Will ask him what exactly it was knocking on tmrw and post.
Hi there. Took to...