I imagine Cecil Sharp (all his recording equipment) must have been quite posh as was the well-educated Vaughan Williams .
Martin Carthy and countless other folk performers accents probably sound quite posh when compared to mine
The point is - it takes time and effort to learn and sing a song and if a posh person does so, fair play, I won't knock'em if they do a bit of chanting, but if they try to take the piss out of "our" songs and tradition by childish parody or trying to take the piss in their posh manner I tend to get a bit shirty.
Mind you Rambling Sid Rumbold/Rumpole (spelling?)used to make me laugh as did a couple of British comedy actors of that era