I'd say the first step would be to get a mechanic in the back of you car to listen to the noise, just spinning the wheel on mine on the ramp didn't trigger any noise, had to be under load and at motorway speeds.
Ended up with a tech crawling all over the back seat on the M60 for him to work out which side it was, apparently the sound deadening doesn't help. He said that the main dealers use a microphone setup clipped to various points on the suspension to isolate, his method proved to work also
