"Ebay would refund all fees for certain listings that ended between 11:15am BST and 8:45pm BST on Sunday 14 September."
That's not the point is it?
If you had a listing that ended during the outage it is quite possible that you received far less than you otherwise would have due to the inability of large numbers of people to bid. Some sellers might have lost hundreds of pounds.
The only honourable thing to do would be to cancel those sales and re-run the auctions for free.
As someone pointed out here on the day, not everyone was blocked from bidding. Mobile app users were still able to access the site and bid. They may have grabbed themselves a bargain, but a lot of sellers are going to be very unhappy with this latest outage.
The internet urgently needs an alternative to Ebay.