Free Man
My take is that John Lennon was being ironic using his acerbic wit to criticise working class people becoming middle class after having been humiliated for many years.

One friend that lived in London for years told me that in UK there is a strong class structure & sentiment and that you can not jump easily class after acquiring a few money. Like if there were "watertight" barriers between classes.

He gave me the example of David Bowie that despite being elegant and millionaire was identifying himself as a working class. From Maiden camp, I can easily picture Janick or Steve say something similar.