Hi Shona
Sarah Vernon is a difficult one to crack. I haven't done it. I do have information that may lead to further research.
In the 1841 census for 15 Canal St, Paisley there is a Campbell family: Daniel (aged 30), Mary(30) and Archibald(9).
0n the passenger list of the Duchess of Argyle there is a Cambell family: Daniel(aged 31), Mary(32), Archibald(10) and Daniel(4).
In the ships surgeons report it says there was 7 births.
On "Denise and Peters" passenger listing it gives the names of the following families having children born at sea: Gollan, Naysmith, McConochie, McDermaid( born & died at sea), Robertson, Wallace and Wilson.
The Auckland Police census of 1844 &1845 has Daniel & Mary living in Fields Lane with 2 children, Daniel being a shoemaker.
The Beresford St Congregational church baptismal register for 1844 has Marion, daughter of Daniel & Mary Campbell.
In the 1849 register of the Free Presbyterian Church the following Campbell family appears:
Archibald born 1842, Paisley
Marion Jane born 1844, Auckland
Children of Daniel from Paisley born 1811 and Mary McKnight his spose born 1809 Paisley.
Daniel born 1838 and Sarah Vernon are missing.
I'll await your comments before continueing. Do you live in NZ?
Bryan