Back home and acess to the 'net. Amazing detail you've managed to dig up, Ruskie. Was going to PM this to you, but somehow seems impolite given the efforts you're going to.
No additional family information that I'm aware of - I think one or another of my aunts must have done some digging, cause I remember half listening to discussions when I was a kid (including the stuff about the death certificate) but I wasn't really paying much attention. I need to ask around as to who is holding that info.
I can confirm you've got the right "Esther". The on-line NSW register of Births Deaths etc provides a very few details, including year of death and parents given names. Presumably the full records (which cost money to access eeerrk!) provide more detailed info. Esther Myles died in 1950 at (or was registered at) Hamilton (suburb of Newcastle NSW). Her parents given names were Daniel and Mary.
Robert Wilkinson Myles died Hamilton 1948, parents listed as Henry and Rachel.
I'll feed your info into the family meat grinder - I'm sure there's someone with fewer expensive and time-consuming hobbies than moi who would like to take this further.
Thanks again
John