>Every single country in the world that is on metric today had to switch from something else at some point in the past. Why overfocus so much on UK when you have literally a hundred successful examples?

A huge percentage of those countries didn't have established industrial bases, infrastructure, etc. And also no educated general populace that needed reeducating. And often those countries were effectively forced into adopting metric through colonization and/or invasion.

Even then, that still leaves most of Europe.