The Karori Cemetery in Wellington has a gravestone inscription for Ellen wife of Revd J Dumbell b.6 June 1831, d.10 Nov.1903, and also for Revd John Dumbell b.12 Feb.1830, d.28 Sept.1923.

The marriage cert will also give her father's name and occupation so that she can be identified in earlier censuses.

I found them on Ancestry in the 1861 census - don't know why they didn't show up in Findmypast. Living in Oldham where William Davidson Dumbell was born. And with John T Dumbell aged 1 (Ancestry index has 9 because of lines scribbled on the entries - think wrong).

Birth cert:
Name: DUMBELL, John Thomas
Registration District: Haslingden
County: Lancashire
Year of Registration: 1859
Quarter of Registration: Apr-May-Jun
Volume No: 8e
Page No: 104

John Thomas Dumbell is in NZ records - married Martha Ellen Mitchell in 1888 - was in Wellington in the 1919 electoral roll.

Sue