The police will likely not pick up on reflectors when your driving as you both have your lights on. The reflectors are for when your parked and a backup for if a light fails. I guess as these look a lot like standard lights just a bit darker perhaps the MOT people are just thinking there standard and not even botching testing them. Though not having them is illegal and will defiantly fail a properly done MOT.
PS even if the police do pull you most likely you will only get a verbal warning, perhaps a fix it not or if there really grumpy a £30 fine with NO points. Not exactly the end of the world