This will explain how to cancel your label, if purchased with eBay, and you may need to wait 24 hours for it to appear before being able to void it for a refund, then print the label again.
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 - 21 days to process.
@louiselee88