Two possible helps in making your population estimates of port city prostitutes
might be found in:
Frances Finnegan, _Poverty and Prostitution: a Study of Victorian Prostitutes
in York_ (Cambridge: 1979), and
Ronald Hyam, _Empire and Sexuality: the British Experience_ (Manchester: 1990)
Curious thing to consider prostitution a type of "labor" per se. I think that
Finnegan will strongly disagree with that assumption and will make a very
good case against it.
Good luck,
Ken Hendrickson
Sam Houston State University