I bet the owner would be delighted to know you've posted his reg on the internet whilst mentioning you took it for a blast and that it's needed a repair. Might be best the blank the plate out
In a quick car, I do... All work done on the car will be road tested to make sure its done right. If you've got a drivers car and (not being picky here) its a younger lad doing the work he's gonna put his boot down on the road test. Aslong as they dont use much fuel or do any stupid amount of miles then go nuts, just dont tell me how fast you were going in it...I think it's more the principal that people are getting riled up about. If you entrust your car into the care of a bodyshop/workshop then you don't expect their employees to be taking it out for a joyride.
If there is a valid reason to road test a vehicle that's one thing, this is usually carried out by a senoir tech or a workshop foreman not any old apprentice or helmet working there. Alot of places take a very dim view of that sort of thing going on and it would result in a disciplinary for misconduct.
If the owner or someone they know spotted it out on the road being thrashed by one of the staff it's going to result in alot of awkward questions.