Sojourn in New Zealand
This phase of the Barlow family's life is rather hazy at present but I will continue to research how, why, when and where they lived in New Zealand.
So far I have evidence of William in England in 1851 as he and his children appear in the 1851 census which was taken on the evening of 31st March.
1851 Census return (31 March 1851)
Master and Mistress of Marylebone Workhouse, London
William Barlow, age 47, born Wigan, Lancashire,
Hannah Barlow, age 45, born Leicester, Leicestershire,
Monitor in the Model School for Boys of the Institution, Chelsea
William Barlow, age 15, Labourer,
25 Carlton Hill East, Parish of St Marylebone, St Marks
Margaret (14) Mary (11) and Eliza (9) Barlow - all pupils, all born in Scilly Isles
I believe Willliam took his family and went to NZ sometime between late 1851 and 1852. 
The next substantiated evidence I have is when his wife Hannah died in Battery Point, Hobart in 1853.
So, I need to search for shipping records and electoral rolls in New Zealand.