Ok I just got back from The UK Today... It was my honeymoon.
Oz is a cool place to be. Just dont expect the same amount of things to do, ie theres all the same things to do just less places to do them as far as the usuall bar, pub, nightclub, shopping sort od thing.
Sydney is good and will remind you a lot of home... Tourist oreinted,and expensive for what it is kind of stuff but none the less good. Oh yeah look up Jacksons Rare Guitars while here. Its just one shop but there's nothing in Denmark street/ Tinpan ally that comes close. If you dont just look like a homeless bum they leave you alone and you can just walk around, pickup a vintage guitar and just start strumming. Its pretty cool.
Brisbane good but not much there you just missed "schoolies week" thats when it really goes off. Travel further up north to see the best of Queansland.
Melbourne this (unfortunatelly) is the most interesting state in Australia. Its definately the most "going off" place in Oz.
Perth, my home town. Fantastic cleanest most friendly place on Earth. Just dont expect anything exciting. Its small and theres not much in the way of youthful exciting things to do.
Of course all this depends on what you like and what you want to do.
Fell free to e-mail me if you want. Perth is obviously my specialty but hey every body i met in the Uk was so helpful this is the least I can do.
Except for customs...god that annoyed me. Anyway.