I'm not a resident of GBR, but I've studied their licensing system.
As I understand it, there are now two different licenses, the Firearms license and the Shotgun license. If all you're going to own is a single-shot or double-barrelled shotgun (or ten) you get a Shotgun license. If you want any other kind of firearm (centerfire or rimfire) you need a Firearms license. You also need it if you want a pump-action shotgun (magazine capacity limited - I think - to two). No semi-auto shotguns are allowed anymore (I could be wrong about that.) Semi-auto rifles are also verboten, except for rimfire, though they may have outlawed those as well. If you want an AR15, it's a 'bolt-action' - pull the trigger, pull the charging handle. Pull the trigger, pull the charging handle...
To get a license you must belong to an established shooting club and/or have proof of access to an area where you can legally hunt. You have to have character references from (I think) at least two upstanding citizens. You have to prove that you have a secure place to store your firearms AND a SEPARATE secure place where you can store your (limited) ammunition.
The police can refuse to license you for pretty much any (or no) reason.
It's expensive. Being licensed opens you to unannounced inspection (though that doesn't happen much (yet)). Violation of any rule can get your collection confiscated and your license pulled. No one but you can have access to your firearms. If you're dear mum knows where you keep the keys to the gun safe, you've just violated the rules.
It's pretty draconian.
Oh, and no handguns except for blackpowder muzzle-loaders.
Someone from England tell me if I got anything wrong.