Barry,
Just to complete the picture see the link below for info available on Aussie BMD certs. They may be twice the price, but they have more than twice the info.

http://www.jaunay.com/bdm.html

Dave

Thanks for that John this is very helpful. Barry

This is a possibility I think the name Thecla may have been mistranscribed

RHODES THELMA I
Registration number 14800/1916 
Father TOM W
Mother THEELA L
Area ASHFIELD NSW

Also have you tried the TROVE site for newspaper reports or the Ryerson Index for death repots

Bev

Also found a death for a Douglas Rhodes

RHODES DOUGLAS
Registration number 339/1935 
Father TOM W
Mother THECLA L
Area ANNANDALE

So that is 2 possible children.
Bev

And a possible marriage in 1940 for Thelma

7359/1940 
CRAWFORD
SPENCER WILLIAM
RHODES
THELMA IRENE
SYDNEY

Bev

Thanks for those Bev, How did you find them I tried all sorts to try and find any children of my grand uncle. Barry

Hi Barry
I got the information from here
https://familyhistory.bdm.nsw.gov.au/lifelink/familyhistory/search;jsessionid=4D147C9C1413F38A31B0C8A4CE151B7E?0

Sorry for the delay in replying a storm blew my internet.

Bev

There is also a newspaper report here about the death of Douglas Rhodes in 1935 he died from tetanus and was 12 years old
http://trove.nla.gov.au/newspaper/article/236475538?searchTerm=%22douglas%20rhodes%22&searchLimits=l-decade=193

Bev