The mixture of metric and imperial comes because the metric system was defined by Napoleon’s government at the beginning of the 19th Century. We already had our own system, and weren’t going to adopt the French one (we were at war with France at the time). Eventually, the metric system came to be the standard for scientific use, because all the units are related to each other by powers of 10, so Britain joined the metre but everyone still used imperial for everyday use. Eventually, metric became the standard for international trade and then the weights and measures Act compelled shops to use metric for most things, except stuff like beer and milk.
Also a Brit and a Scot??? My Grandfather might have been a proud Scotsman, but he was definitely British!!! Ditto my mother in law.