Info on Mary Ann, daughter of Thomas Tandy.
Thomas Tandy arrived at Otago port, NZ, in 1838 (1) (2). According to his daughter Mary Ann, he arrived on the Magnet, which made several trips between Sydney, AU and Otago in 1838 (3). It is quite probable that his purpose was to work in the whaling station at Waikouaiti. A key point here being that he came out of Australia.
On 30 Aug 1843 he married a Maori woman, Maria Manaha, at Waikouaiti (4). He may have had a prior relationship with another Marori woman.
The birth of his dauther Mary Ann Tandy is not registered at the NZ BDM historical website, but this is to be expected as she was a half caste child. In a 1909 news article Mary Ann states that she remembers being christened 69 years ago (1840) by Mr. Watkins in the old (Wesleyan) Mission House. She was then presumably five years old. In a later article, from 1929 (9), which quotes an interview with her in 1919, it states that she was baptised on 24 Mar 1844 and that her father was the Swede Thomas Tandy. The 1844 date should be correct as Rev. Watkins was in charge of the Mission House 1841-1844.
Mary Ann was probably born about 1839 and Maria may have been her step-mother. In the book 'Invisible Sight' (5) she states: "'Being the daugher of a Maori woman and another being my stepmother' Mary Ann Tandy claimed, "I am entitled to their land as it was bequeathed to me by them before they died. I have made no injuiry into this matter as I left the Maoris when my father was lost, and have been among European people ever since.'"
Who the "European's" were that raised her is unclear. Thomas Tandy married Bertha Gorham in 1845 and he was lost/died in June 1852. Mary Ann did not marry until 1859, so the years of 1852-1859 are unaccounted for in her life (assuming she was with her father and Bertha 1845-1852, which might not be true).
Info on how to request records from the Methodist (Wesleyan) Archives at
http://www.methodist.org.nz/files/docs/amy%20scott/otago%20and%20southland%20districts%20baptism%20registers.pdf but be advised that the archives are still closed as a result of the Christchurch earthquake.
Mary Ann is mentioned in a news article in 1909 (6). You will also find reference to her land Petition dated 1885 (7), in which she identifies Thomas Tandy, an Englishman, who married a Maori woman, as her grandfather. It should perhaps read father and that he was a Swede.
Mary Ann Tandy married Andrew Thompson in 1859 (Reg No. 1859/1464). Andrew died 20 Aug 1894 (

at their home in Waikouaiti. He was 75 years old and buried at St Johns Cemetery, Waikouaiti. Mary Ann died in 1929 (death reg 1929/7008), at the age of 93 (birth year approx 1836) and was also buried at St Johns. (St John's Church (Anglican), Beach Street, Waikouaiti)
(1) Web site "Pre-1839 foreigners in NZ " at
http://sites.google.com/site/pre1839settlersinnz/index-r---z (2)
http://freepages.genealogy.rootsweb.ancestry.com/~nzbound/magnet.htm(3) Foveaux Strait Trade, 1838
http://www.nzetc.org/tm/scholarly/tei-McNOldW-t1-body-d1-d14.html(4) BURIALS & WEDDINGS FROM WAIKOUAITI REGISTERS. 30th Aug 1843 Thomas Tandy to Maria Manaha
Waikouaiti. Witnesses Hannah Watkins (&) Joseph Crocome
(5) From Invisible Sight (
http://www.aupress.ca/books/120170/ebook/05_Angela_Wanhalla_2010-Invisible_Sight.pdf)
(6) 24 Mar 1909 article at PapersPast mentions the loss of her father
http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=OW19090324.2.51&srpos=6&e=-------10--1----2thomas+tandy--(7) Reports of the Native Affairs Committee, 1885. No. 64.—Petition of Mary Ann Tandy, Petitioner, who is a granddaughter of one Thomas Tandy (an Englishman, but who married a Maori woman), asks to have her maiden name enrolled on the Maori record kept by the Government. I am directed to report as follows: That the petition should be referred to Government for inquiry. 16th September, 1885.
(

PapersPast, death of Andrew Thompson
http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=OW18940823.2.54&srpos=1&e=-------100--1----0%22Andrew+Thompson%22++WAIKOUAITI+mary--(9)
http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19291204.2.129&srpos=1&e=01-01-1929-31-12-1929--10--1----2mary+Ann+Thompson-ARTICLE-