UPDATE:

Just received a response from eBay.  Case is now closed with the following:

"We've reviewed your case and have decided to issue the buyer a refund of £55.00 without any impact to you.

This case is now closed. You aren't required to reimburse the buyer or eBay and this case will not be counted in your seller performance evaluation."

I also see the funds have now been released to me.

So sounds like it should be sorted out now?