To update my findings so far (in respect of asking for advice on the job seeking process from overseas (and needing a job offer to get a visa)):
KiwiCareers (UK Down Under recruiter) - Responded asking to see CV to give further advice. Place candidates using Skype interviews.
Datacom (Round Peg Recruitment on their behalf) - Responded asking to see CV to give further advice. Accredited Employer and advertise for overseas candidates.
WorkingIn - just post the job adverts, sort it out with the Employer.
Enterprise Recruitment (UK Down Under recruiter) - Responded asking to see CV to give further advice.
New Kiwis - Responded, suggested to get CV completed and would meet when in NZ. Provided Kiwi style CV example.
NZSkillsInDemand - Responded by saying they were more Construction based. Advised that it is possible to secure a job from overseas but being in NZ is better.
So, basically, first step is to create a Kiwi style CV, even if you're just looking for info.