Ask the buyer to open a "not as described" return case for the item on their My eBay Purchase History page, and to choose the option "Arrived damaged". You should respond on the case with the postal tracking number and state that according to Global T&Cs you are not responsible for loss or damage in transit after it has arrived safely at the UK hub.
If you have any issues with that contact ebay using callback on here:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
