Are there any specific conditions, i.e. turning, breaking etc... I agree with the above, 99% going to be anti-roll bar bushes, could also be track control arm bushes. Also check the break calipers aren't moving undeer breaking (if you are hearing the noise under breaking) I have heard of cases where calipers have come loose, and move around!!! - This happened to a friend of mine, and the caliper fell appart on the M1