Under 16 CFR § 500.8, metric-only labelling is illegal in the US for many categories of consumer products. Does any other country make metric-only labelling illegal?
1. beer and cider (not e.g. wine, spirits or non-alcoholic beverages) must be sold by the pint, half pint, or third of a pint (strong beers and at tasting festivals mostly) when delivered "draught" ie they pump it into a glass, rather than handing you a can or bottle.
2. milk can be sold by the pint in re-usable containers (typically glass bottles for the purpose). I'm not sure this is actually mandated by law, but since it depends on the containers even if it wasn't you can't easily switch.
3. precious metals like gold, silver and platinum, are sold by the troy ounce.
The Brexiteers would probably like to push harder on this, but they're old and their "brave" economic experiment is a colossal failure, so "Let's make things worse" went off the agenda pretty firmly, now it's all about rescuing some sort of dignity from the mess.