I actually know a way he could have shipped it, but he probably wouldn't want to pay that much.

Freeze the black pudding, flash freeze if you have access to a commercial flash freezer. I don't know what the shops would be called in the UK, but here in the US you'd go to an industrial supply company like Granger, grab a styrofoam cooler as the "box", grab some packing peanuts as filler, and purchase half a pound of dry ice. Seal that up and the food can be in transit for up to 1.5 weeks without worries.