exactly back woodsman , it is irrelvant whether you or i like the style of the singer i do not like PEARS or worse still cliff s arrangement of   the water is wide, but it is still a folk song.and would be considerd so by most people, likewise brigg fair
there are some old songs that are defintely folk songs,there is a general consensus, it is not just my opinion
i acknowledge that with more modern songs, in which it is debatable but that is hardly relevant.