To cut a story short:
Car went for MOT.
They took wheels off for a brake inspection and to upsell brakes.
Refused brake work, collected car, drove 40 miles, wheel fell off.
RAC attended, none of the wheel nuts had been fastened.
Car back to MOT place for them to inspect damage and replace wheel etc.
They changed the brakes and nothing else 
Now convinced it's not merely a mistake it's negligent so who do I report motor safety to?
If anyone works in the industry even better!
Thanks in advance.