Thank you to everyone who has commented
on this.
I had completely forgotten about the 100 year rule!!
I will contact the NSW Records about obtaining a
Birth certificate but am unsure about how best
to obtain this as I'm in the UK- presumably I'd have to
provide some sort of legal document to prove who I am?
Ros- Caroline Waller was my Step Great- Grandmother
and this explains why my Mother was named
for her and not Christina who was Mary's Mother( my sister is
called Christina)
Billy Thomas also worked as a general Handyman
although on the passenger list to Australia he is listed as a Mining Engineer
and this is certainly what he returned to doing when the family went back to
Wales in 1934.
Mary was a cook/ Nursemaid and ,I believe, initially lived in
Balgowrie with her sister and brother Bill Sellars -Renwick who ran a bus company.
I have a copy of Billy & Mary's Marriage Certificate but it doesn't have addresses on it so may be
in shortened form and I visited St.James's Church last time I was in Sydney.