@Gerry-And-Rashid0, @James73, Yes guys you are correct there. Basically there are 2 angles to check into; one is what are the regulations that you need to comply with and what are the regulations/laws/by-laws that someone is claiming you are breaching or non-compliant with. Don't accept a generic cover-all such as "you are breaking the law" or "in breach/you can't do that."
As Gerry and Rashid are saying; ask the person or corporate rep' for documentation to demonstrate their claim.
In the meantime proceed with caution, keeping an eye on existing regulations which you can access. Most councils have these doc on their websites and they are very long, but down load a copy save it to your files and get reading.
Once your bookings are confirmed, keep a copy of your contact information. If it's not a commercial transaction, you can still honour the reservation if you need to take action to avoid prosection, and do what you feel is needed to maintain the commitment you mmade to the people who put their trust in you. You will no doubt make very good friends out of the situation. You cannot be prosecuted for letting friends visit.
By the Way, this is not legal advice on my part, you would need to exercise your own judgement and discretion.
Good luck, keep us posted.
Christine.