If it won't let you cancel contact ebay tomorrow and ask them to do it.   You can ring them or request they ring you by viewing this link on your phone - not on a laptop or PC:
https://www.ebay.co.uk/help/eua?id=5190

You should probably put the buyer's ID on your blocked bidder list:
https://www.ebay.co.uk/bmgt/BuyerBlock