Norman Penty, who did so much research into William's family tree, traced Frank's progeny to Mark Wasson and Stephen and Kent Warner who live in Sydney. If anyone knows them, I would love to make contact.
The only other Australian connection I have come across is that William read Catherine Spence's Clara Morison but declined it with a letter similar to that he sent to Charlotte Bronte on reading The Professor.
Thank you so much, Australian cousins, for getting in touch. The picture in filling in a fascinating way.