I want to say that Metrification came into English everyday life over several decades. Certainly the WWII blueprints were Inch, or the trouble the US had helping England would have been worse. The English still drink beer in Pints (but not US Pints). UK argued with EU to allow some traditional units in labeling and signs.
I have long been puzzled by American gallons which are only 6 pints compared to an imperial gallon which is 8 pints. I always thought everything in America was bigger but clearly it is not.
Best way to size-up a Pint is to go to England and order a beer.
By the way, does anyone know where to find those small isolating plastic beads (or know what they are called) that are used in the busbars?