I'm gonna go out on a limb and say there are old Labour voters who also prefer the old system.

It wasn't a poltical issue in Canada
It's you that's making it political. You and everyone else associating this with Brexit, or with Tory voters.

To be clear, I know the metric system is superior. Well, it is for everything except miles. We're so used to miles that it would be a huge upheaval if we changed that one, it would require cars to be adapted, signposts around the country to be replaced, it wouldn't be worth it. Not knowing how many yards in the mile is completely irrelevant, since we just say 4.5 miles or whatever. I know a mile is 15 minutes walk, I immediately have a good idea how far somewhere is if we talk about miles, while in km I'll need to do some mental gymnastics, at least if it's a large number. I can estimate but I'll be off a bit, for example London is 240km away, not 220 like I suggested earlier. At the age I'm at, I can easily adapt, but probably not if I'm an old bugger losing my marbles.

Miles is used for long distances, nobody needs to know how many meters it is to London.

And I'd rather buy a pint of beer than half a litre, but that's more nostalgia than anything else. They're more or less the same amount. Although if we changed that, we'd probably get ripped off. I doubt it would be slightly cheaper to buy half a litre of beer than a pint, so that's 10% of a pint fleeced.