While it is true that the magnetic field encompassing the Earth is not a sphere and dips inward at the poles, there is no reason a standard compass would not tell you which way is south and which way is north. While doing a google search for compass zones and which one to use for where, I got an astounding number of results for GPS calibration and pretty much nothing for standard analog compasses. There was one(1) sailing forum [www.cruisersforum.com] in which a user mentioned the need of "zoned" compasses for travelling below the equator. In one post. Thats it. If the need for "zoned" compasses were real, there would be a lot more information available on the internet.
If the worry is getting completely lost in the blue mountains or similar, I would think bringing a good map, gps, x-tra batt., compass, and a good working knowledge of orienteering would be paramount.
I have to agree with Willeke on this one, he's got experience. Both Sources given by the OP in his answer are from the same website, "mapworld.com" The wikipedia source cites mapworld as the source for that info. Mapworld is a RETAILER OF COMPASSES IN AUSTRALIA AND NEW ZEALAND.