I also didn't know they were called cob nuts. In my part of the US, where they're grown commercially, they're hazelnuts, but I understand that in a lot of the US they're filberts.

I had to look up images of Waitrose cob nuts to see what you meant by still with their hats on. Around here, if you buy a bag of them, you get just the nuts themselves, unless you're buying chocolate- or candy-coated ones.