Or, to be more exact, they are over the Channel. The original Green Wellies were made by Hunter near Dumfries. Unfortunately, the company had financial difficulties in 2006 and was restructured in 2008 as a manufacturer of fashion accessories for the svelte of calf. Their boots are now made east of Suez. The replacements of these lesser offerings on the quality Green Welly market are Le Chameau and Aigle which are French.
This is somewhat ironic. The not-so-heroes of the Crimean War gave us Raglan sleeves and Cardigans. The French were on our side; so, sense of style permitting, they can share. The victors of the Waterloo Campaign gave us stout footwear: Bluchers and Wellingtons. What about Napoleon? What of the French? Oh dear, this can only end in unspeakable puns on defeat and who got the boot.