I am descended from Harriet through her second husband, Stephen Stacey. I have transcribed details of her death certificate and second marriage cert. On the marr. cert. she says her father's name is John DOWNER. The death cert. says she was born in Plymouth, but I think the informant must have got the ports mixed up. I would think Portsmouth is more likely, as there are many Downers around there, but none that I could find in Devon.
Harriet was said to be 84 when she died in 1915 (birth c. 1831), and to have married for the first time at 20 (c. 1851). Her first child, Harriet MARNER, was born in July 1853, supposedly on the voyage to Australia, and doesn't seem to be registered. Unfortunately, the death certs contained very little info in 1863, when William MARNER died, supposedly at the age of 60 (birth c. 1803).
I have not been able to find corresponding marriage details for them on FreeBMD.
Didy