So sorry not to have gotten back earlier to thank you all for your much-apreciated additional work -- am in a different time zone (obviously) so went to bed, and then had a doctor's appointment in town first thing.
Rosball, I enjoyed reading the two newspaper articles you found. To judge from the professions of Capt Davies' colleagues listed as co-signatories in the Cockatoo convict island piece, it looks as though there was some sort of significant building works going on there at the time. And it was very interesting to read the types of different costumes people chose for fancy dress at the Mayor's Ball (which appears to have been attended by hundreds of people!).
MAJM, thank you for your further thoughts pursuing why David's baptismal record may not have yet come to light, and for the link to PDF about Paddington and suggestion to try e-mailing Woollahra Local History Library. This is most useful.
Sparrett, Thank you so much for taking time out to check that David wasn't attributed by mis-transcription to wrong parents in light of Mary's also being born in 1856 -- I'm still having difficulty accepting that he truly existed as Owen Davies' and Jane's child. There are a couple of references in slightly later-dated family documents to the number of children this couple have, and David makes one too many! I think that he must either have died as a baby/toddler or for some reason not have been brought up by this family.
Y'all have significantly expanded/potentially expanded my knowledge of Captain Owen Davies' time in Australia -- I am most grateful to you.
I have very much enjoyed my time with you!
Thank you all again so much.
CELTICANNIE