I've seen an unregistered uzi - the owner is a former 'banger who is now grown up, and gone straight, but he doesn't want to part with it.
And last week, I was at a pub having dinner, and some fellow saw my KCR t-shirt, and started telling me that machine guns were illegal, and he knew so, because a couple of years ago he paid a fellow $700 for a full auto SKS... I had to restrain myself from telling him (a) that he shouldn't talk about that sorta thing to complete strangers; and (b) that he got ripped off.