Hi
You could also try this link.
http://www.childmigrantstrust.comFound mention of an Estelle Yates not sure if she is your Estelle or not but it had a date of birth.
Government Gazette
Western Australia
Public Service List 1956
Land and Survey Department
Assistant
Estelle Yates
Born: 12 July 1939
Date of appt: 5 December 1955
Cheers
Tania