"the location almost certainly being the Hawkesbury River in Australia"
A moot point Richard
Prof. Bob Thomson researched the song and linked it to Oxborough Hall, on the banks of the Rover Ox, where there was once a settlement of returned Australian transportees.
The song is definitely very popular in East Anglia
I agree totally about it being composed from experience
I believe that Banks of Sweet Primroses, obviously an attampt tp present a failed love afair from both points of view, is a superb example of folk composition - largely the exuberance of a young man 'feeling his oats'   as we used to say in Liverpool, drawing a blank and resolving to look elsewhere - full of symbolic references rather than description
Way beyond the abilities of a desk-bound hack
Jim Carroll