Just in case anyone is wondering about this it seems it is fairly common for universities and other similar institutions to offer graduate diplomas and/or post graduate diplomas which are seemingly what I described above as a post-baccalaureate degree (waiting for confirmation from several places now).
I'm finding the NZ terminology in this regard a bit confusing to puzzle through, but each institution seems to have a web page (which can take some finding!) on their site dedicated to definitions of what all the PGGDip/GDip/certificate/diploma stuff means (for that particular institution!) and requirements for acceptance into the programmes.
So maybe I'm not the only one who gets confused...