I'm a little surprised that a folksong singer and a neofolk singer were asked what song (note, not what "folksong") best describes Englishness. Is there a subtext here that popular music is no longer English?

Most here who have actually tried to suggest such songs have not used folksongs as examples, perhaps because by definition folksongs address matters in the past and therefore provide roots for the present, and illuminate human nature and by analogy the present, but do not directly address present conditions (although the Jute Mill song and William Brown both show very close analogies).

The social structures that provided for most broken-token songs and other songs of love lost and betrayed are happily almost wholly vanished. Ploughboys are gone (although I recall the verse added by the Young Tradition
"There's a boy on a tractor a-going like hell
And what farming is coming to sure no-one can tell")
So are shantymen, the pressgang, and flogging round the fleet, dowries and killing one's daughter's suitors (well, mostly). Infanticide is rare.