"I am 53, and know for a fact that no one younger than me would have used imperial as part of their UK education, and anyone who does is doing it as an affectation. Like that twat Jacob Rees Mogg."
According to https://ukma.org.uk/what-is-metric/uk-progress/uk-metric-timeline/
"1974 Maths teaching in metric in primary schools is now the norm – science has been taught in metric since the turn of the century."
That's around the time JRM went to school.
Like you, I was also educated in metric and much prefer it. I'm fairly bilingual in metric and imperial for linear measures but for areas and volumes I normally try to stick to metric only. Unfortunately I've got an American client who is in the habit of mixing fractional inches, decimal inches and millimetres :( on a single page of a document.
Incidentally there seem to be quite a few conspiracy theories around the introduction of metrication in the UK. Quite amusing .... or depressing?