I heard scraps of this story from him a few times, but I could never quite figure out exactly who the ancestor was, or even whether the cow went by rail or sea. Perhaps Garret didn’t know. Anyway, details will have to await further research.
Whatever about the traveling dairy, it is clear that, long before the era of Ryanair, or even before the era of direct car ferry services to the Continent, the family in which Garret grew up moved in a world of easy interaction with France, and other countries on the European mainland.