Here is how to receive a refund for the postage labels not used.
They may take 24 hours to appear before you can void them.
Find your label with this link . https://www.ebay.co.uk/ship/lmng/labels-history/seller-hub and to the left of the sales record there is a drop down menu under 'Actions' click on that , then click on 'Void Label'. The refund will take between 5 - 7 days to process.