JHW, So are you happy to sing lily the pink or god save the queen or were all going on a summer holiday at a folk festival or at a folk club, as lomg as you do it in a folky style[ what exactly is that is it singing like frankie armstrong or like bob dylan OR LIKE JOSEPH TAYLOR]

I have seen you sing many times and you have obviously considered your repertoire first and foremost, i have heard you sing tam linn,i have never heard you sing bachelor boy.or any cliff richard songs
methinks you are playing devils advocate. any person who thinks anything goes as folk, as long as it is acoustic.and done in a folky style[whatever that is]is imo misguided.
any singer makes judgements on what he is about to sing on two things whether he likes the words or the tune or both, that is a repertoire judgement not a stylistic judgement.
they then subsequently decide to sing the song in a certain way that is a stylistic judgement.
so based on this argument to put style as more important than repertoire is a nonsense
when peter pears or cliff richard
sings water is wide it does not cease to become a folk song, you may not like the style but it is still a folk song, same tune same words,

when leadbelly sang a blues version of prickly bush eg [gallus pole] ,it was still a folk song, regardless of whether you like the style