Just thought worth posting here a recent surprising experience with a Royal Mail standard International parcel. The parcel was sent to South Africa and the buyer told me it didn't arrive so I eventually refunded and claimed from Royal Mail.
Royal Mail have just been in touch to deny the claim and provided a tracking number which they told me showed delivery to the address. I was surprised that any tracking number existed and when I looked it was not visible in the usual places in Click and Drop (where I bought the postage) or passed across to ebay like it usually does if I mark a tracked order as dispatched. Finally if I put the number into Royal Mail's tracking page I get nothing after the original collection but 4tracking.net gives me the full tracking details to the address in South Africa.
I did eventually work out that the number is actually on the original shipping label below the barcode. So the lesson is, if you ever get a claim of non-receipt on an international standard parcel bought online, download the postage label again and see if there's anything that looks like a tracking number on there. If there is, try it on 4tracking.net and see what comes up.