There is no restriction on the number of shotguns that can be held on the authority of a shotgun certificate.
The only requirement is the shotguns be stored securely, so adequate security measures must be put in place.
Some gun-cabinet makers designate their products by a notional capacity ? a five-gun cabinet, for example. This does not mean you cannot store more than five guns in it. It is the actual capacity of the cabinet that counts, usually twice the maker’s designation.
As much as 5kg of smokeless powder may be stored.
There is no requirement to keep it in a locked box as with black powder, but common sense says it should be stored away from heat sources and made inaccessible to children.