You say that businesses & customers should have to have a choice
Well they say that, but they don't really mean it. After all, why should laws just stop at what units are used to sell shit by ? Why not scrap the laws around what additives you can use. Or about allergy labelling - or indeed ingredients labelling ? After all, shouldn't manufacturers be free to sell what they want, and let consumers decide ?
Ultimately, the chances of the UK somehow reverting to mandated imperial measures is the square root of fuck all. The closest we will get is to change the font of the existing laws, and sell that as a "Brexit Benefit" while hardcore Brexiteers scrabble around to find someone to read it to them, and an Express headline that uses the word "Brexit", "Quaking", "EU powerless", "unlocks" along with a quote from Ben Habib.
Meanwhile normal folk will continue to use their dual labelled measuring jugs and scales however they most feel comfortable as they plop the 250g of mince they bought from a shop into a recipe that calls for half a pound and wonder what all the fuss is about.