Americans don't claim to use imperial weights and measures; they use customary weights and measures, which were also used in the UK prior to the creation of imperial units with the Weights and Measures Act 1824.
EDIT/CORRECTION: Milk is sold in multiples of 568 mL, so while the quantities are pints, the measurement is metric.
What distinction do you intend to make by that? 1 pint is 568ml.
If you mean in labelling or something, no, they're marked 1/2/4 pints. Usually also with litre markings. You can also get metric sized bottles, i.e. on the supermarket shelf you'll often see one brand's 2 pint bottles next to another's slightly smaller 1l bottles.
The supermarket price labelling will be in £/litre, regardless of whether the bottle's pints or not, if that's what you mean?
Kilograms seem more and more common for human weight too though, largely driven by fitness apps & communities I think. I doubt children in school today are accustomed to stone; only pounds and ounces for birth weight perhaps, but even that is metric medically and converted for the parents' familiarity these days I believe.
Fraid not.
No medical professional in Blighty weighs people using imperial measurements. The only people who really use them are the elderly and (bizarrely) the type of crappy slimming magazine seen at supermarket chekouts...... The kind satirised by Viz as titled "Less Cake, More Exercise".
Not really. Old people might cook with funny old temperatures/measures and weigh themselves in stones, but it's fading out, contemporary cookbooks and gym culture are all metric. I've literally never seen a utility bill in anything other than metric (even if it's slightly weird metric like kWh or cubic metres of gas).