It is against board policy, which you agreed to before you posted, to name other members. So your 'warning' will shortly be irrelevant.
Instead, you should have cancelled the sale with the reason 'buyer didn't pay'. That way you get your fees back. Then you block them.
Simples.
All it takes is a few minutes reading up on how selling on eBay works.
Edit: You've been a member for 13 years, do you really not understand how eBay selling works?
