i guess! i dunno. trade unionism was very important to my family and something that working class people where i live have pride in, even if its more of an inheritance than an active thing to the majority of people of my generation, i would expect working people to have heard of, if not observed, may day in some way.
maybe thats different for different places in the uk and different age cohorts, its probably one of those dastardly lived experience things again.