Dear Alice,
No such thing! The assumption that there is a Northern and Southern system of BaZi is pure nonsense.
This is because BaZi is based on the constellations (which are the same whether you are in the Northern or Southern hemisphere), NOT 'climate' of the country.
I've started my consulting career in Australia, way before moving my practice back to Asia. My strong base of Australian/New Zealand clients that are still with me today, are testament to the ONE unified system approach to BaZi.
Hope this helps.
Warm Regards,
JY