Not aimed at you Chris, as I've no idea what delivery company you use, but basically it's the race to the bottom that causes this kind of thing. MyHerpes are the cheapest, nastiest couriers, along with Yodel, and they give a cheapy nasty service. As soon as I find out a company uses them then I stop using that company, same as I used to with Sh*ttyLink when they were going.
I'd rather pay a couple of quid more for a decent service than risk everything, and it's situations like this that reminds me why I do that. And in fairness to Marzman, I do get caught out on occasion when I forget to ask what courier or get caught up in the moment and impulse buy, so no blame aimed at him either.
Arguably you could simply go to court and fight on the balance of probabilities, and I might even be tempted to send a letter saying that to the seller and see what happens.