I'm sorry to disagree Mr Happy, but he was breaking the law there.Actually that's not quite right Shotgun. I know a man who's the armourer for several police forces and a guest armourer here and there who's got a collection of weapons that would make you wince. Churchills Tommy Gun, one of the MP5's that went into the embassy, Sten Gun serial number 00005 etc (and when I say etc I mean 100's of weapons)
All quite legit on his section 5 firearms license. I may have told this story elsewhere on ARRSE once but I was on a range day and I approached said armourer and said something along the lines of "I can't help but feel the Steyr Aug would be better than these SA80's" and he produced the barrel and then the body out of his armourers bag at his side and said "like this". My jaw hit the ground.
He would have a section 5 for his work, transporting weapons from place to place and the like, and he might even have a dispensation for firing various bits, but only for testing purposes. The various bits that he owned himself would be on his section 5 but only for the purposes of either collecting, as historic arms, or arms with historic interest. Most of what you say might be correct if he was using official licences for testing purposes, but if he was firing his 'own' stuff on auto, or if he was firing them and they were capable of auto fire, he would be breaking the law. I think it more likely, if it was legal, that they weren't his and were part of the police forces own collection, which I think unlikely, and had taken them out for testing purposes on official documentation. The only other way is if they were deacts. Going out fopr jollies with police kit is a no no, and firing your own even under a section five is also a no no unless it has official sanction and purpose.
That's all different from owning and blasting away at a local club as a private individual.