From what I see and read, the Brit's went the route of having metric rammed down them wholesale, without regard for the fact that there were a lot of legacy uses for the old stuff. Made it difficult if not outright illegal to get and stock materials in english sizes, etc. Or at least, uneconomical for the material producers to do so. End users have to pay and pay. Not that thta is any different anywhere, mind, but it seems more the tradition there.
Canada went wholesale and enthusiastically (at least the government did) metric in the 1970's. Now they are teaching Imperial measures in school again, as there was a time when all the new engineers had to be taught what feet and inches looked like so they could deal with drawings of installations already in place. :-)
The US has laws on the books dating to the time of the US Civil war era, that make doing business in metric units legal, but it was never sucsessfully made mandatory. Economic realities are slowly making it hard to avoid the stuff in the US, as you have to be able to deal in metric sizes to fix anything on your domestic vehicles now.
Cheers Trevor Jones