There are positives and negatives here.
You may not actually need to apply for a visitor visa, if you're a national of a visa waiver country (which I'm guessing you may be as you're currently in the UK).
http://glossary.immigration.govt.nz/...eCountries.htm If this applies to you, you simply fill in a form on the aeroplane as it approaches NZ.
You certainly can apply for, and obtain, a work visa from within NZ.
On the other hand, entering as a visitor, you are assumed to be going to leave again, you need a return or onward ticket, and you don't get an immigrant's concessions if your belongings arrive before you get your longer term visa.