Again, thank you everyone for your help. I have looked up all the birth entries as noted by members; Matilda Jane (1865) Margaret (1868), William (1870) John (Deazley 1872) and Thomas (1874). The older children, Elizabeth (1857) James (1859) Catherine (1861) and Anne (1863) fall before the beginning of records.
Could I ask if anyone has come across obviously inaccurate records? The marriage cert of the parents, John Deazley and Margaret Park (22 April 1856) states that their respective fathers are Joseph and John. I think the writing is fainter and in a different hand from the foregoing details on the certificate. I am sure that John's father is James (died 1877 on GRONI), hence the name of the eldest son. There are no Josephs in the family. Margaret's father was Alexander Park (died 1869 and registered by John Deazely). The last child, born after arrival in New Zealand, was called Alexander as a consequence. One can never be too careful, but the scarcity of 'Deazelys' and the fact that John and Margaret were illiterate weighs somewhat. Alas, the New Zealand birth certificate of Alexander gives a different marriage date - and in 1858, not 1856, but that was recorded in 1877, after 20 years.
Regards