I'm a native, I'm an Aucklander but today I flew to the South Island for the first time in my life, I'm in Dunedin at the moment.
In Auckland I normally use 400; it's versatile, I can use it indoors too without a worry, especially with the f1.8 Yashinon on my Lynx.
Outdoors 400 can be overkill, but the Lynx 1000 is again quite useful as it has a 1/1000 speed and can stop down to f22. I've never needed both at once though! I lived 7 years in Brisbane, will be going back in July for a wee holiday, so I can certainly understand why 400 might be trouble there
You could probably get away with 100, but there'd be a few borderline situations, especially if you get into the wilderness much. If it were me, I'd go with 400 just to be safe, but then again I'm new to analogue and therefore have a childish love of grain :P