Not sure about the info you have received, true you will most probably not secure a job before you are there. Think about it, there are 1000's of accountants, so they want to see you in person - makes sense really. It's not like a special skill set that would secure you something from the otherside of the world.
As for jobs - there are plenty, go on Seek.com.au and do a search for accounting roles for your and OH's postions. Both Melbourne and Sydney will have more jobs than Brisbane.
We started of choosing Melbourne and then changed our minds, probably the best city in my opinion but the weather is a bit up and down and we dont like the beaches there.
Sydney is just another big city and we are leaving London, so want a change - though it has nice beaches, but property close to the beaches is expensive and by close I mean walking distance.
My OH does not like Brisbane - no real reason.
So we went for Perth, never been there, so we will see. But we can afford a property within walking distance to the beach.
Oh and I am an accountant just in case you thought I was being negative about your career choice. The agents I have spoken to have all said the same, no chance of getting a job from the UK but no chance of not finding something when you get here - just be FLEXIBLE on the first job and then the next one will fall into place.
I think you should decide where you want to go and then research that city, all the big cities have plenty of jobs for accountants.
Good luck