Soldato
You don't need any reason to own one and can own as many as you like. You'll need a reference merely to confirm your identity (like for passports) and to state they don't see any reason for you not to own one. I got my boss at work to do it.
A safe is a good idea but again I don't think it's compulsory as long as the shotgun is 'secure'. I may be wrong I already had one to keep my £1000 air rifle in.
The local FO's visit is to physically check your security, and that the guns you have are the same as the ones on your certificate.
When I asked a few years back they said te safe is compulsory and you must not hand over the keys to someone without a license EVER that means that you should always open the front door if the safe key is on the same ring. I was also told the ammo has to be stored and sealed away seperate to the gun but that may of changed in the past few years