Re: Sidney Chapman Plumstead London abt 1878
We have a Mary Adelaide Chapman born in Plumstead - not sure what year, but probably 1880s.
She may be related to your Sidney unless there were a great many Chapmans in Plumstead (sorry, don't know London geography).
Do you have a record of any cousins of Sidney?
Just in case it helps, here's the rest of the story:
By 1903 Mary had come to Australia and was married to Peter Livingstone in 1906. Early photos of the couple in 1903 show her looking in her mid-20s to late-20s.
They lived in both Wellington, New Zealand, where their eldest daughter Winifred Flora was born and then Sydney, Australia, where their second daughter Joyce Gwendolen was born in Gosford.
Joyce and Win grew up at the large family home at Kensington in Anzac Road. Peter and Mary lived there until they died and left it to Win who died in the 1970s - then the property was sold.
Hope this gives you a lead,