Thank you all so much.
The Australian connection was very recent with the discovery of Kate's Birthday Book, so I am still exploring Australian genealogy sites.
I knew they must have gone after 1883, because their eldest daughter, Elizabeth, married that year in Wellington, but have been unable to find them on passenger lists. Guess it's a case of trawling. (Well, I've done that before.)
William (death cert 1916) lived in NSW 29 years and NZ 30 years - he was a carpenter, born in Cornwall.
Elizabeth (death cert 1913) spent 26 years in Sydney and 36 years in NZ, born in Staffordshire. BTW, her maiden name was Elizabeth Hall Webster, which clears up the confusion over surnames mentioned by Cando.
I had seen the marriage with Matilda de Prideaux, but I never connected. On William's death cert she is referred to as Matilda D. Prideaux. All I had on Matilda was a reference in Kate's Birthday Book and on William's death certificate. I can't find her birth anywhere - must be NZ, but I couldn't find it on the Index.
I had been under the impression that Matilda never married - the family story goes that she was engaged, but went to NZ to visit sister, Kate. Took one look at the state of her marriage and swore off it for life! Maybe the story refers to Jane Maria - who never married. I have a photo of 'Aunty Tot', which I had been led to believe was Matilda - but maybe it was Jane Maria.
With the information you have all supplied, I may be able to find out what happened to them.
NSW bdm was up and running late this avo - I found Edward William married Margaret Smith in 1904.
BTW, my interest in this? William and Elizabeth are my great great grandparents. Their daughter, Kate, my great grandmother.
Although, it's interesting how history repeats - 100 years later, I followed them - and have no intention of going back