This is a really tricky question to answer as 'living comfortably' is a very subjective point. I'm a Brit living in Melbourne with my Aussie husband. He earns more than $150k and I recently gave up work (1st baby due any day). We rent a 2 bed (tiny) house in Elwood, a popular Bayside suburb, at a cost of $400 per week (not the most expensive suburb but not the cheapest either). To buy our tiny house would cost $650k so renting is cheaper unless you can put a large deposit into the mortgage. We like going to the movies, don't scrimp on quality food and veg at the market, run one small 2nd hand car, have a very nice dinner out once a month and we just make it by every month after bills etc with a bit of savings (for those VERY expensive flights home to the UK)...though I add I have been back once in 2.5 years.
You could do it cheaper if you live further out of the city centre...but DH and I HATE suburbia...over here it really is quite suburban anywhere other than the close city suburbs but you will only learn that from coming over and renting. Lots of folks LOVE that 'Neighbours' Melbourne 'burbs life but we don't.
One other important point to note is that schools in the cities (Melb/Sydney) are heavily focused towards private education and the gov't here has let state schooling slide to really low levels (esp secondary level). Upper/middle class families here think nothing of spending $8k for a junior school place per year rising to $15k plus per year for secondary schooling, and they make major sacrifices to afford it (there's also a lot of snobbery around quite surprisingly). The schools issue is a key factor in why I will be dragging my DH and children back to the UK at some point.
Like another poster said, if you have a lot of equity in pounds this will set you up nicely, but don't think that when you get here and are earning Aussie dollars that it's cheaper; in many ways I have found it more expensive...and I lived in London prior to coming out here.
Have a look at www.realestate.com.au which will give you a rough idea of the price of houses to buy and rent in all areas of Australia.
Conversely to you, I have done our sums and reckon my DH could earn substantially more in the UK than he does here (he works in IT) and that financially we would be better off living in the UK.
That said, I don't want to put you off, I've had a great time out here for nearly 3 years now, and we will stay for another year or two. Living overseas brings you many life challenges and experiences that you would never get staying in one place for your entire life.
Good Luck!