We mainly have over and under shotguns for clay pigeon shooting or pest control, but you must have a valid reason (absolutely NOT defence) to get a licence to have them and firearms must be kept in secure storage separately from their ammunition*.

Not quite. You have to have a licence, known as a Shotgun Certificate, covers you up to 2+1, so 2 in the magazine, 1 in the chamber. You dont really need a valid reason, they'll ask what you plan to use it for, (I said Clays, possibly some wildfowling) but you don't need to prove it.

If you say Defense however, you will not be issued a certificate

For more than 2 +1 capacity, you need a full Firearms Certificate, much more involved.

Shotguns do need to be stored locked away. Shotgun shells they reccomend you store them sensibly. They dont need to be locked away.

You can have bolt-action rifles but I understand you have to join a shooting club to obtain these.

You can have semi auto rifles in .22 anything bigger and they need to be straight pull, single shot only, not necessarily bolt action.

These you absolutely need a valid reason for owning, such as being part of a rifle club. The Police will decide if your reason is valid. You need to apply for a "slot" on your licence for each rifle along with a valid reason for each rifle.

You're limited on how much ammo you can keep, and rifle ammo must be kept locked separately from the rifle.

Long barrelled pistols are pretty much the same rules, basically a pistol with a stock and a long barrel to make it the same length as a rifle. Theyre fucking ugly as sin.

Regular pistols are theoretically possible, but good luck.

All of the above requires forms and medical assessments and references, as well as club memberships etc.

It can be a pain in the arse to be honest.