A wood buring stove is a goodly heating option for your area. Especially if you put a wet back into it to heat water.
If you have the land area you can try the ground based hydronic heating/cooling option but it is based on pumping water through kilometres of pipes buried nearly a metre down.....big $$ to install and possibly operate since it needs to be pumped. Also works best as an underfloor heater.
Simpler, slightly cheaper version involves burying a few long lengths of 150mm+ PVC pipe 600 to 1000mm down and blowing/sucking/convecting air through into floor vents in the house.
Incidentally, some weather stations on the BoM site have soil thermometers down to 1m depth....here's the link for Victoria http://www.bom.gov.au/products/IDV65176.shtml
Sun Lizard (or similar toys) is another great heating/cooling option for Nthrn Vic.