Hi!
i've been working in nz for the last couple of years. you must register first and start asap as it's a lengthy process! you could apply for a working holiday visa which lasts one year and prevents you from taking a permanant job or you get a job offer first and then apply for a work visa which lasts for longer. with this visa if you change jobs you have to pay for a change of conditions of your visa but that's relatively straightforward. or you could apply for residency which is more expensive and more involved but you wouldn' have any restrictions on working - it's quite difficult to qualify for residency. check out the nz immigration web site - that should give you all the info you need - don't bother ringing the embassy in london - it will cost you alot of money and you'll get through to an automated message. the csp also has advice on working overseas - just ask them for their nz handout. there's heaps of jobs!
hope this helps
anna