@Liam47
Try airbnb again using a direct message to @airbnb help on twitter.
Refer to their own rules stating that you may cancel when a guest is breaking your house rules or you are uncomfortable with the guest. Refer to the commuinity center as well. This person is clearly not suited for house sharing.
Be factual and polite and include the booking number.
But before you do anything of the above, tell your guest through the platform messaging board. Something like "after numerous reminders regarding house rules with no improvement, you are now going to contact airbnb in order to terminate the booking".