It is perfectly doable and indeed many do so.
Some estates and shoot owners / organisers/ guides do have their own RFD for this very reason and will safe and secure storage for many of their guests.
Cornerstone of many gunshops business is storing guns for their clients.
And perfectly doable to get a friend to get a rifle / shotgun and put them on his own ticket.
As to using the guns in terms of licence.
Simplest is to use them in the presence of a certificate holder. Gets a bit complicated though.
Shotgun Certificate holder can use any shotgun, indeed can borrow one for a period of three days without notifying the Police. Can hold as many as his security allows. Makes it easy enough for a SC holder to accompany a visitor to a shoot and visitor to use the gun in his presence. Often at the bigger shoots with overseas visitors “loaders” are there for this very reason.
Firearms Certificates- are much more restricted in that a certificate holder can only use the rifles on his ticket. And rifles - it serial number that is critical. A non certificate holder can use the rifle under the the close supervision of the certificate holder, provided the certificate holder has the lawful authority to use the rifle on the land in question.
Overseas visitors can also get a visitors Firearms Permit. This needs to be sponsored by a UK certificate holder. This does allow you to acquire and use a firearm in the UK. So when applying you put down the details of the rifle that the visitor will be borrowing, and the visitor can then use / transport it etc.