The problem I have is that the burning of the Wicker Man is very popular in this day and age.
Does that have to be a problem, provided, of course, no people are getting burned in those wooden cages (which they're not, to the best of my knowledge), and the act is merely symbolic?
As for the "powers-that-be" giving us a day off, as you say, May Day has long been celebrated in this country, but has only relatively recently been a national holiday, brought in, I think, in either the late '60s, or mid-'70s, when Michael Foot was Employment Minister in one of the Wilson or Callaghan governments, and inspired by the May Day celebrations in the then Soviet Union. Nothing more secular than a Marxist holiday.
So I'd be inclined to put a more positive spin on the recent examples of wicker man burning that you cite. I see in it a certain defiance of the prevailing culture - both our formal and historic Christian culture, and the de facto secularised one that has gradually supplanted it. I see such ceremonies more as an assertion of ancient traditions and customs, a conscious echo of our pagan past, than anything more sinister, and something entirely divorced from the "powers that be"; more a bottom-up expression of ancient religious impulses.
Not my cup of tea, but where's the harm?