Sorry to thread-drift after all, but is Martha, the Watercress Girl definitely by Clifton? It doesn't appear in BL or the Oxford library catalogues (only Watercresses from this thread). (And I think I wrongly said above that Roy Palmer made this atrribution; I think I was misremembering that). It is attributed to Clifton in other threads here and elsewhere, but I can't see any confirmation.

And if you're collecting watercress songs, Levy has The London Water-Cress Woman (pdf link) (1831), which, according to a note in the song, used the actual melody that the watercress woman used for the words "Come buy my watercresses".

Mick