Open an unpaid item case 4 days after sale date.

That gives buyer a further 4 days to pay and if they don't then close the case.

The buyer gets a strike on their account and with 2 or more they cannot bid or buy from ebayers with blocks in place.

You get the fee credited back, neither can leave feedback and you can relist.

Also them to your BBL so they can't do it again in the future.