We tend to do a lot of mixing and matching depending on circumstances here. Pint of beer, two litres of Diet Coke, that bag is a kilo of flour but that woman weighs nine stone seven pounds. My ribbon is 5/8ths of an inch wide, but the beads to go with it are 8mm.
Cooking tends to be the splitter for old and younger generations using metric or imperial. I use ml and g/kg for preference, but I can pretty much get by fine if a recipe is in pints/oz. My mum will only ever use pints/oz, and my nieces are only learning ml/g.
I don’t mind using anything, as long as it’s appropriate for the purpose and not just flipping for the sake of it. I can convert mph to km/h, but I don’t bloody want to, unless I’m driving abroad.