How much would it cost me to travel in australia for 3 months?

My fiance and I are planning on travelling around australia next year for 3 months. Is there anybody who has done this or knows someone that has.
If anyone could give me a rough estimate on flights, accomodation, and spending costs, i.e food etc.
We plan on staying in a few hostels and cheap hotels etc mainly along the east coast.
Any help greatly appreciated.
Sorry, UK. Any airport.

wouldn't we need to know where your flying from?

Check http://www.hostelio.com/australia/ and click on the cities you are planning to travel. It will show you the cheapest hostels...

Try to find an average price for hostels in different cities and multiply it with 90 days...

You can manage to have a rough calculation of accommodation costs by this way...

I think air asia has a flight to KL,Malaysia and then to Aus,try that.
Also emirates,ba,qantas,singapore airlines,malaysia airlines all have via flight from uk to aus.