@Darren19
I would call airbnb 02 8520 3333 and tell them you are in fear for your guests safety. I would also call the insurance company and find out if you are even covered should this guest fall down the stairs. Do not count on airbnb for any insurance.
At this stage, I would just cancel this guest through airbnb if possible and delete the profile altogether and start over again. Deleting the profile is the only way to get rid of these cancellations on your page. If this is your only booking you have a chance to do that now. You are beginning SEVERELY behind the post with all these cancellations. If a traveller has no confidence that their booking is secure 9 times out of 10 they will not book with you.
Keep your listing on snooze and find out how the site works before you go live. Turn off instant book until you are more experienced and have your house rules and so forth fine tuned. When you go live you will get a boost to the top of the search for a short amount of time - do not waste it - as this is an opportunity to get bookings to establish some reviews.
Good luck.