Well tightened the bolts on my car, on that 'u' shaped piece of plastic part 3.
Then set off, oh no noise worse
Then realised the boot roof protector wasn't latched, either up or down
So set off again, no rattle, then heard a slight bump, so grabbed the passenger seat belt in frustration and gave it a couple of yanks.
Now, all quiet on the western front, problem solved.
So thanks to ManiacGT