eBay are only giving you the address and postcode that the buyer has entered for their delivery purposes, so the issue with the incorrect postcode lies at their end.
Have they perhaps entered an 0 and not an O? Is there the required gap in the postcode, or does it all read as one ?
If it needs correcting any simple mistake may not be obvious at first, and could have been made, send them this link to amend the address:
There are 5 addresses which need to be corrected
https://accountsettings.ebay.co.uk/uas/addresses
If you enter it into Google maps what does it show?
@sstmor_0