In answer to the last part of your question, to my knowledge, in most countries you would have to change your student visa to a work visa as soon as you graduate. Therefore, it would make sense to start looking for a job or professional internship during your last year of school so that your employer can sponsor your visa.
Not sure what the IT job market is like in NZ. Hopefully, someone else can answer that. But it's so gorgeous there, I'm not sure how you're going to concentrate on studying! Just kidding - good luck!