A little bit of history...
Aotearoa - the Maori name for NZ means "land of the long white cloud". The first Polynesian people arrived around 1000yrs+ ago (still being debated). They were a different people culturally from the modern Maori - many of whose ancestors arrived much later (in open canoes!!). The first European to "discover" NZ was the Dutch explorer Abel Janzoon Tasman in 1642(?) unfortunately he didn't land... well, he tried to but the local Maori weren't impressed and they had the landing party for dinner (unfortunately for them they were the main course). This event occurred at the top of the South Island - near where the Abel Tasman National Park is located. It is speculated that Abel Tasman first sighted the peaks of the Paparoa Range before heading North. He partially mapped the West Coast of both Islands - though he didn't realise they were islands. Thus the possibility of a great southern continent persisted in Europe (to balance the land masses in the Northern Hemisphere!). Captain Cook rediscovered NZ over 100yrs later (1769) and got on with the locals better (or maybe he didn't look/smell particularly edible - actually cannibalism was not widely spread in NZ and, even then, it often occurred as ritual of battle - so Abel was unlucky). Cook found the Maori to be a non-hostile people with considerable diversity between the tribes he visited.
Cook's visits narrowly preceded those of French explorers and NZ could have easily become a French colony. However, the first European settlers didn't arrive until 1840 - making NZ one of the last countries to be colonised by Europe. Prior to the settlers there were the whalers many of whom lived with the Maori.
NZ was never conquered by Britain, rather a treaty was signed regarding sovereignty and law (there's an interesting extract from the then British Government on the web). This treaty is the basis of NZ government today. The early settlers relied on the Maori for survival and initial relations were relatively good. European diseases, Maori tribalism and a different concept of land "ownership" led to a few problems in the second half of last century and early this century. The introduction of modern weapons also changed the tribal balance of power. The World Wars claimed many lives - both Maori and European. One in every three NZ men between 18 and 40 were killed or injured in WWI - a higher proportional loss than any European country involved. (The world wars marked significant set backs in the history of NZ mountaineering and exploration). Post WWII saw a movement from a rural based society to an urban one - most Kiwis live in the main centres; Auckland, Wellington, Christchurch and Dunedin. The move to an urban society has proved to be the greatest threat to Maori culture and tribal life. The most recent arrivals to NZ have been from Europe (after WWII) and more recently Polynesian peoples from the Pacific Islands. The latter make up a significant proportion of NZ's population, the Samoan community is particularly large. Auckland is the largest Polynesian city in the world - often with more islanders living there than in their homelands. Currently NZ is enjoying a resurgence in Polynesian culture, particularly Maori. Although NZ has a European heritage it is a mistake to say that there is a European culture. Although there are few pure ethnic groups, NZ is still very much multi-cultural and the threat of assimilation of indiginous cultures has subsided in recent years.
The Government is currently attempting to redress wrongful land confiscations last century. Unfortunately, the Conservation estate - which covers some 30% of New Zealand's land area is an easy target for quick solutions. It would be a tragedy if this land were treated as a commodity for economic return, not just for New Zealanders - the international importance of the unique wilderness and wildlife of New Zealand is currently recognised in two major world heritage sites - South West New Zealand and Tongariro.
There's probably far more history elsewhere on the Web!