Been thinking about places where Brits still use imperial and what sort of trouble it would cause to change it.
The main contexts I see imperial units in are certain body measurements (in feet & inches as well as stones & pounds), volumes of milk and some types of alcohol (in pints), and road distance signs (in miles).
Body measurements are basically in the process of switching over; many younger people (including me) would always measure their weight in kilos and would likely not understand stones, for older people stones are still the predominant unit. Height's more complicated, some older people would only know it in feet and inches but most people I suspect would know both feet & inches and centimetres – perhaps with varying priority though, I would use both depending on who I'm talking to without considering one more primary than the other. Do note that this is specifically personal height and weight, not other uses of those units which are mostly metric.
Milk is basically always sold in integer numbers of pints, but bottles will list both pints and litre. Sometimes you see companies try to change to litre bottles (1.76 pints) but then they, clearly accidentally I'm sure, sell them for the same price as standard 2 pint bottles which never goes down well; I suspect this is the main reason milk hasn't switched over, though it's not an unsolvable problem (I personally food shop mostly based on price per unit rather than item price for almost everything which is always £/100ml or £/litre for liquid). Alcohol (specifically beer and cider I think) also has a similar problem with pints though I don't drink so I don't know much about it (though interestingly wine I buy for cooking with is usually labelled in cl rather than ml).
Road signs are by far the biggest use of imperial units here. Width and height restriction signs use both imperial and metric (though weight restrictions have been fully metric in tonnes since 1981). Distances for cars are in miles and I honestly can't see that changing for a long time; I would personally use km for distance on foot, but for cars everything's in miles. Definitely not an impossible change (Ireland finished metrication by changing speed limit signs to km/h in 2005) but not one I can see our government doing any time soon.
The main purpose of the metric system is to ease conversions between units and honestly given that personal measurements are already well on their way to being fully metric and that milk bottles will always have a metric price per unit labelled on the shelf near them, it's not really that bad. You don't need to convert units when you go down to the pub to get a pint, or when both speeds and distances are in miles anyway. Now, let me just put 20 litres of petrol in my tank and then check my fuel efficiency to see how far that'll get me, should be simple enough right…
