It looks as though Sydney is likely to be their location, but with a surname OWENS, difficult.
I would suggest that you contact try contacting a Newspaper - possibly -
http://www.smh.com.au/
Here they are in 1958:
Former address = 5 Kingsley Close, Dill Hall Estate, Church
Name: Bryan OWENS
Date of departure: 6 March 1958
Port of departure: Southampton
Passenger destination port: Sydney, Australia
Passenger destination: Sydney, Australia
Date of Birth: 11 February 1940
Age: 18 (calculated from DOB)
Marital status: Single
Sex: Male
Occupation: Son
The following people with the same last name travelled on this voyage: -
Ellen OWENS DOB: 12.2.1917
Roona OWENS DOB: 11.8.1941
Yvonne OWENS DOB: 24.11.1951
Beverley OWENS DOB: 18.5.1953
Ship: CASTEL FELICE
Where bound: Australia