@Joshua289
It can be very awkward to confront a guest about breaking house rules. Many friendly people will suddenly become defensive if caught out and take their resentment out on you, or leave bad review because they then suspect they are going to get one too.
If I was you, I would take some preventative measures. In my experience, it is much easier to get guests to agree to follow rules while they are trying to book with you, or if they think you might cancel the reservation (most guests are not aware of the cancellation penalities for hosts).
So, make sure you include in your house rules that no one outside of guests on the booking will be permitted on the property and this is Airbnb policy. If guests want to have additional people stay or use the facilities, they need to adjust the booking to the correct number of people and pay for them.
I would also state that there is CCTV at the listing and that guests who appear to be breaking this rule, i,e. if any unregistered people are seen entering or leaving the property, they will automatically be charged for the maximum number of people and an additional cleaning fee. Of course, you need to know what your registered guests look like for this to work. Do you meet them on check in?
You need to make all of this crystal clear in your house rules, also because you are more likely to get back up from Airbnb in a dispute if you can prove that the guests broke rules that you had listed.
I would also make sure you reiterate all of this before a guest books or as soon as they book if using IB. You can phrase it very politely: "Just a gentle reminder that it's against Airbnb policy and my house rules for non-regestered guests to enter the property, so do make sure you include the correct number of people on booking, even if they are only visiting for the day. It is much more economical than having to face penalty charges later!"
I would also find a way to remind them before they come that there is CCTV. You could say it's "for your own safety as well as my peace of mind that no one other than the guests are entering the listing".
I do hope you sort this out. It's really important. You do know that having unregistered guests there can invalidate any claims you might need to make under the Host Guarantee?
