what bureaucracy? most of europe, UK included, has very strict gun laws. it doesn't matter what the gun's status is in the US, you get caught with a gun here, you're proper fucked. it's not an issue of not filling out his papers or some minor shit like that, it's a serious offense.
i mean in my country, getting caught with a gun will absolutely land you in jail. the only exceptions are having a permit for sport shooting or hunting, but the law requires the gun to be locked in a designated box literally at all times unless when used at the shooting range. obtaining the permit means mandatory classes on safety, passing psychological tests, all sorts of pain in the ass tasks. and even when you technically have the permit to have it (and really, the law says you are permitted to store it), if you're caught with that shit in your pants they will charge you as if you didn't have a permit at all.
it's no joke.