Not quite correct, you cannot fire a Bren, Sten etc in NZ unless you have what is known as a "theatrical licence" which is for making movies & re-enactions & then ONLY blanks.
NZ has a basic firearms licence that covers all "sporting arms" you can get "endorcements" on that licence to own/fire certain types
B, Pistol: allows ownership & firing, limited to 12 handguns.
C, Collectors: allows ownership of pretty much anything but NO firing.
D, Dealers: self explanatory.
E, M.S.S.A.: (Military Style Semi-Auto) allows ownership & firing of SLRs, AK47s, AR15s etc in their original configuration.
B,C & E require permits to purchase plus additional security etc
When it comes to purchasing 'A-cat' firearms (which covers the SMLE etc) you can walk into a gunshop, show your licence, pay & then leave with the rifle, no need to inform anyone in authority & no restriction on numbers owned.
I can be back at home after a auction, posting my latest purchase for all to see, within 4 hours of bidding & its a 2hr 20min drive home.