Sorry Im coming in even later Id suggest we follow the Auckland Urban Area as defined in Statistics NZs  Regional Summary publication at least until their approach for the  Census becomes clear This area is divided into four zones Northern Western Central and Southern Auckland Profiles of the zones including links to maps are listed here The Auckland Urban Area includes the Hibiscus Coast Kumeu Ardmore Papakura and Drury so it encompasses Papakura as well as the four main city councils and stretches beyond into the Rodney and Franklin districts It does not include Pukekohe Waiuku Waiheke Helensville or Warkworth which are the other urban areas within the Auckland region or Muriwai which is classified as a rural centre