Went out tonight with my girlfriend driving, me sat in the back.
After about 30mins of messing about, AND eventually folding the rear seats down at 40mph and climbing into the boot
I reckoned it was coming from the rear wheel arch (as smitd004 previously suggested, so thanks for that!!
So, the investigation continued. I made my way back to the rear seats and fastened my seatbelt
I then waited for a long stretch of empty road, with no other cars in sight
, and opened the rear drivers side door, at 45mph, when the noise was present.
I managed to work out that the noise is definitely coming from the wheel arch area
, and the reason for thinking it came from the roof is because the noise came into the car from the boot, and was heard over the top of the rear seats - hence making it sound
like it came from the top.
So, once I get the god damn wheel nuts ripped off, after some *** at the garage put the locking nuts on with a windy hammer, hence too tight and bent wheel nut key, I'll take the wheel off and inspect the wheel arch.
For now my mind is at rest because I've pinpointed the noise to a specific area...
One question / concern though: There was a horrific smell of burning clutch when I opened the door at speed, and also hanging around the car when we got home! My girlfriend is a good driver / doesn't ride the clutch etc, plus the smell was coming from this OSR wheel! I opened the bonnet, no smell there. Any ideas?
I'll update you when I get round to inspecting this further after our weekend away, thanks so much for all the help & advice (and to my girlfriend for driving up and down one stretch of road for an hour