If you didn’t know about it, this guy Nick Le Mouton has put together a pretty extensive list of postcode information for New Zealand, available here <https://www.noodles.net.nz/2007/09/14/new-zealand-postcode-database-v2/>. There are details on 43457 streets in 1260 suburbs with latitude/longitude positions, and separate tables of rural delivery addresses and P O boxes/private bag locations.