Hi DubbieBoy and welcome. First off I suggest you join the Dunedin Aquarium and Pond Society. They will probably have lots of plants etc to offer along with help and advice re the local scene. Their secretary is Colin, in Mosgiel, phone 489 7270. For further contact details check out our Homepage under "Clubs". A full contact list is there.
http://paul.aaquaria.com is an excellent site and he also sells plants on TradeMe. Very knowledgeable and based in Feilding. Is also a member of this site.