A decision was made in 1965 to adopt the metric system but no government has ever had the guts to completely get rid of the old Imperial system so we have adopted a weird half-and-half scale of our own. It's not Imperial, and it's not Metric. It's Britric, it's perfectly simple, and it works like this...
Legally, you can only buy fuel or fizzy drinks in litres, but draught cider or beer must be sold in pints. If the bottle is returnable we buy milk in pints. If the bottle is non-returnable, we buy milk in litres.
We weigh sugar in kilograms, precious metals in troy ounces and ourselves in stones. We measure all goods sold by length in centimetres and metres ... and then transport those goods on roads measured in yards and miles.
When the weather is hot we talk in Fahrenheit, because the number is higher and sounds more impressive: "Wow, it was 86 degrees today!" When the weather is cold we talk in Centigrade, because the number is lower and sounds more impressive: "Wow, it's -4 degrees today!"
Want to make a hamburger? You'll need to ask your butcher for 113.398093 grams of beef so you can make a quarter-pounder. Cake recipes will talk about grams of dry goods, and fluid ounces of liquid.
Ships sail in knots, racehorses run over furlongs, football pitches are measured in yards and rugby pitches are measured in metres. Land is often advertised by the hectare (but it's officially registered in acres - at least until now) and if you phone up to order "a ton" of something, you might get a ton, a tun or a tonne!
Then again, we also use the Standard Comparative Index, by which things that are difficult to imagine are compared to things slightly more easy to imagine. It runs: pinhead, fingernail, matchbox, house brick, a football, a human man, family car, double decker bus, Jumbo Jet, Belgium - as in "they have destroyed an area of rainforest the size of Belgium." This is despite the fact that no-one from Britain has a clue how big Belgium is. An alternative to Belgium is Wales, but no-one who isn't from Britain has a clue how big Wales is.
Somehow, it all works. So, will Britain ever go the full nine yards (8.23 metres) and go completely metric? Never! It would be far too confusing...