A good machinist with the right information and materials can easily make even the most primitive projectile tossing weapon from ordinary and unconventional materials. And building a basic shotgun is simple.
I have seen a tire iron drilled out and modified to fire a .22L.
The answer is to not make more restrictions and laws. Give everyone a gun, make it mandatory. There will in the near future readily accessible materials that will allow anyone to make a weapon, and maybe in 10 years or so a person could get a laser and power supply from other equipment, or a phaser. Are we going to keep mankind hobbled by restricting access to technology?
Give Britons full access to guns I say, what are the officials afraid of, a country full of idiots with bruised egos about who can shoot the best all having duels with each other trying to defend their honor?
That is the purpose of nanny government, right? The things you talk about make mother pelosi want to get her ruler out and rap your knuckles.