Milk bottles are still imperial sized, but funnily I more often hear people say "big milk" '& "small milk" rather than pints.

It's actually a real mix. Actually look at the milk you buy, some shops will do half litre, litre etc bottles some will do pint, 2 pint bottles. I'm pretty sure they'll be priced the same. Clever little bit of shrinkflation where 0.5 litres is 68ml smaller.