I let the wife have a drive while I sat in the passenger seat; I was listening out for my rattle/buzz to see if I could locate the offending area/root cause. I found it.
The bloody screw in toe hitch was in the passenger door storage bin!
Will need to call dealer and apologise for being stupid.....
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X3 2.0d SE, Jet Black, Black Nevada, Fineline Wave Wood, Dynamic Pack, Servotronic, Pro Multimedia, Grey Windscreen Band