Hi,
Hopefully your Ancestry sub includes Australia and, as Neale has said, the Electoral roll records will be a help up to 1980. As the family originated from UK, they will have been automatically eligible to enrol to vote in Aust at the age of 21 before 1973 and 18 after 1973.
Establishing their whereabouts and occupations might lead to more findings
Another possibility is a cemetery and search in the Brisbane area.
Sue