Thud sound over bumps

[Judd]

Good evening gents,

My B6 is wonderful in many ways, however when she goes over sharp speed humps there is a singular thud noise from the rear of the car. Initially, I thought the spare wheel was loose, but I've gone through the boot to no avail. It has also been up on the ramp and it has been poked, rocked and bumped every which way to identify the fault but we are coming up with a blank.

This afternoon I rode in the boot (private road obviously officer) and managed to roughly pinpoint the sound to the driver side rear quarter but I cant tell if its the top of the suspension, fuel pipe from the filler (there is movement when you connect the fuel hose to the down pipe) or some black box of tricks.

Anyone got any thoughts?