You know the American left’s hang up with “assault rifles” is very bizarre. In Britain, they banned handguns but AR-15s are still legal (though hard to get), because they view handguns as being the most dangerous.
I am very confused by your post. I lived in Britain and endured their insane gun laws until I moved back to the USA. If I had an AR-15 in Britain and discovered by the police I would go to jail for a long long time. In fact their are very few AR-15s in Britain as they have their own military 5.56 that is not an AR. The British version is a good rifle. The few ARs in Britain are carried by United States Army and Air Force personnel on military bases and they are full auto 3 round bursts. They actually not AR-15s. They are not because they are full auto.
Please elucidate on your post. I am confused.
ps
My next door neighbor when I lived in Britain was a Thames Valley Policeman, we call them bobbies. I inquired of him what would be necessary for me to have a weapon. He explained that first I would need to be a member of a gun club (very expensive), apply for a permit to buy a weapon with an extensive background check (very expensive) and if all was okay I would be issued a license to buy a weapon and ammunition that must be taken to the gun club and kept under lock and key unless I was shooting at the gun club. I told him, "it was not worth the bother." He said, "that is the idea."