I'm 39 and never used imperial weights despite living in the UK from birth until relocating in 2018. I don't even know how many pounds to the stone today without looking it up, and constantly get surprised by all the other Brits who don't think in metric by default (but that happens enough that I do know to multiply kg by 2.2 to get lbs).
Yeah Pounds to Stone is a pain in that it's fourteen while Ounces to Pounds is sixteen. I think the only thing I used imperial for is bodyweight and that's just due to either parents or doctors using it. Other than that we used to ask for a "quarter" of boiled sweets at the shop, but I never internalized what the exact weight was (I guess a quarter of a pound) it's just what my dad taught me to ask for when I was ~4 and I kept it up.