I hear it called a British childhood institution, but I don't know any Scottish folk who ate it as a child. Is it an English rather than British thing?
I think Marmite, did try to market as a childhood institution. In the 1970's their TV ad's had the tagline, "Marmite. It's the Growing Up spread you never Grow Out of".
I'm Scottish and remember eating it for the first time at a friend's house sometime in the 60s- with disastrous results.As a practical joke he neglected to inform me that it shouldn't be spread in marmalade size quantities.Didn't put me off though.I love it.