for firearms Cit, you need to show reason for ownership, for instance having a long range rifle that shoots targets at 1km, i couldnt own it and be a member of a local .22 club that only shoots on a 100m range, which means you need full membership to a club.
bisley is a good choice because they cater everything, its a bit of a travel, but it is a brilliant site.
if you get a Firearms cit or shotgun cit you need to have a bolted down safe, which they will try to rip of the wall to test its properly installed.
there is a bit of a grey area when it comes to shotguns though, as law states that to own a semi auto you need a firearms cit and not a shotgun, but shops wont sell to you with out the shotgun cit, so i got both at the same time, and in turn saved 20quid doing so. which is worth doing, my safe holds 5 guns, so i can only own five guns, and you have to contact who ever issues the cit's to inform them or every purchase you make.
i also have membership to a local gun range, but they are only .22 which is a bit anoying, but im not too fussed because my MP5 is fun to shoot.
and the AI .338 cost about 7-8k second hand, which is why i might instead get the ak and ar15 because its cheaper and more fun

but i just want a big cal because ive had a go of the 1km range and its brilliant, i just want my own gun to play with on the 1km......although ammo is very expensive for the .338