They may work there and as long as you comply with ebay's seller protection (send to the address given via ebay using trackable postage) you should be OK.
But if you're worried you can cancel the transaction. Go to the dropdown menu for the item on your orders page and cancel using the reason "Something wrong with buyer's address". If they've paid a refund will be issued in the process.
And put their ID on your blocked bidder list:
https://www.ebay.co.uk/bmgt/BuyerBlock
