I originally researched for my relative under the Barwell Boys Scheme in 2002, but I did manage to locate his file which was very comprehensive, - for contact details, see below. For a small fee, they will send you a photocopy of all the paperwork, and at the time it only cost about 31 Austrlian dollars.
My mother's half-brother, Tommy Clark, sailed to Australia in 1922 on the Benalla - he came from Scotland but I think the majority of boys came from England.
These are the contact details:
The full information is held at the State Records Office of South Australia. The address is PO Box 40, Enfield Plaza, Sth Australia 50085.
Telephone 08 8226 8000 and firstname.lastname@example.org
However, I did contact someone in the State Library of Queensland where the index for the Barwell Scheme is held. They gave me the file no. and the dates of my relative's arrival, which you apparently need before you contact the office in Southern Australia. This is the person I contacted and her email address (don't know whether it's still current):
Family History Unit
State Library of Queensland
Barbara Kirkham email@example.com
Hope this helps - let me know how you get on.