@Kerry-Phil0, completely unacceptable behaviour. For one thing, they've broken a major condition. Firstly, if you're not able to reach the guests, I'd contact AirBnB and alert them to the situation. There's a contact number at the bottom of the guest's itinerary in your messages section.
There's also this.
https://community.airbnb.com/t5/Tips-Tricks/Contact-Airbnb-A-Community-Help-Guide/m-p/16165/highligh...
I'd then gather up their belongings and put them near the door. Or outside on the verandah.
Regarding a late check-out fee, you can claim this through the Resolution Center.
https://community.airbnb.com/t5/General-Hosting/The-Resolution-Center-A-Community-Help-Guide-Request...
I'd also recommend that you request a Security Deposit for future guests.