What I was wondering is - what are the distinctive differences between Perth and Melbourne

Jo,

I'd be hard-pressed to pick any difference in accent between people from any Australian cities. People from "the bush" tend to use more slang and adopt a more laid-back approach to enunciation (" 'Ow yer goin', mate?"), but that's a rash generalization that will probably get me into a lot of trouble. Anecdotally, the further north you go, the more slowly people speak, the inhabitants of FNQ (Far North Queensland) being reputedly the slowest speakers, but I can't say I've had much experience of them or it.

There are a few local variations in vocabulary across the country. The only one that springs to mind instantly is that people in South Australia refer to an electric power pole as a "Stobie" pole (after the inventer I guess?).