At this stage ebay won't be able to do anything - their money back rubbish only starts Nov 1.  It is a Paypal issue assuming you used Paypal.  Paypal will almost certainly issue them a refund but require them to return the item registered post at the buyer's expense.  Is the item worth a lot of money?  Might it not make more sense just to let them keep it?  Sometimes I offer to let them keep it if they wear the postage cost - this is a particularly useful strategy if you know they are talking rubbish and there is nothing really wrong with the item.