Sydney is by far the most expensive, followed by Canberra, Melbourne, then the rest... I live in Melbourne, I think around A$300k is about average entry level for a 3BR house, of course if you're prepared to live further away from the city centre the prices drop down a lot. domain.com.au is a real estate website here. Wherever you live, it's bound to be a cheaper cost of living than the UK. (N offense).
Thanks
Fabian