First of all, orphanages should be on the census - though sometimes the inmates were only recorded wioth initials.
To find his parents, you need to order his birth cert
Can be ordered online from
www.gro.gov.uk using the ref you have from the indexes, cost £9-25
What I do question, though, is how you know that is the right birth for him? I guess you found him later in life in Australia giving a very specific time and place of birth?
(Oh, Mort, red letters just come up, seems I am probably missing something vital! Will post anyway)