I wish I could provide advice for what to do from here, but eBay are notoriously difficult to communicate with once they make their mind up about something, unfortunately.

You could alsways try contacting PayPal, from the perspective that the refund was unauthorised due to the buyer not meeting the return conditions, and if they won't help, contact the FOS and see if that makes a difference.

This really seems to be a problem ParcelPoint have to address, though, since it is their tracking summary that doesn't actually indicate the status correctly which has caused the problems.