Officially the UK is (mostly) metric, but for everyday 'popular' usage, we are mixed. Speed and distance are miles per hour and miles, but shorter distances are metres. Most people know their heigh in feet and inches, and weight in stones and pounds (but not pounds only). I can think in both stones & pounds, or in kg. Obviously, a pint is a pint (imperial, not American) - milk or beer.
At work (engineering), I have always used metric, including when working for a major American electronics company (which was completely metric).
I expect that many people, like me, are equally happy using imperial or metric.
However, America does not use imperial measurements. An American ton is smaller than an Imperial ton (American ton is 2,000 lb, while an Imperial ton is 20 hundred weigh = 2240 lb - which is very close to one metric tonne = 2,204 lb). Likewise the American gallon and pint are both about 20% smaller than their Imperial counterparts.
Another confusion is what we call a 'thou' (1/000 in), Americans call a 'mil', which in the UK would be short for the metric mm. 1mm = 40 thou.