Last month I purchased a module (through bank transfer, which wasn't clever, seller wouldn't take PayPal), and tracking the package looks like it was sent, arrived in the UK and then was either lost or undeliverable. Royal Mail can't allow me to claim for a lost item until the seller contacts the postal service in their country, but the seller has failed to respond to messages.

Has anyone managed to fix this kind of situation? Best guess, the item is sat at Heathrow with an unreadable or wrong address. It just needs the seller to start the process...

Well... after several calls to various levels of the British postal service (face to face at local mail depot is best) it seems like the item was found and delivered to my office yesterday, a month late.

So, never give up!