A silencer/suppressor/moderator is treated the same way as a firearm over here. Crazy but true. When you get permission to get say a 308, you also need permission to get a moderator for it. In practice it's not quite as hard to get as the firearm, as once you have shown the "good reason" for the gun, you can get the mod.
Our moderators aren't as expensive as yours (£50-£300ish) so making one would probably be more hassle than it's worth. Once we have a "slot" for a mod on our tickets, I don't think it makes much difference whether it's store bought or self made. All my mods were store bo