In the UK we just use both, if you drive down a motorway you’ll see road signs measuring distances in miles, and then another sign telling you that there is 400m to the next junction. Or I can turn to my dad and describe a bit of wood as being two inches by 10cm.
Generally we use metric though, and I’ve not noticed any labourers having problems with the maths.
Mind you, for some reason drugs are often still sold in (fractions of) ounces.
