It's not a scam but could affect your dispatch ratings. If you're worried about that you can ask the buyer to agree to cancel the current transaction (refund would be issued in the process) and relist it on the date they want, for them to buy and pay again.
To cancel click on the dropdown menu arrow alongside the item on your sold list and select Cancel order > Buyer asked to cancel.
Or you could cancel as above but then put their ID on your blocked bidder list so they cannot buy from you again:
https://www.ebay.co.uk/bmgt/BuyerBlock
@with5583