I've been reading these forums long enough to see that weighing up Australia versus the UK is sport around here, but it usually from the perspective of someone moving from - or back to - the UK.
My wife has UK and Aus. passports, but for the past 10 years we've been living in Los Angeles and, more recently, Berlin. For a time, we were really trying to move to London (where we have friends) or Brighton (where we might be more likely to afford). We've been a bit put off by the difficulty of finding a school for our daughter, and since most of our friends don't have kids her age, they wouldn't be able to be much support. Also we have no family in England. But in terms of culture and lifestyle, I think it suits us well.
When we learned that a second child was on the way, suddenly Melbourne started seeming like the more reasonable choice, in spite of the cost of living that seems London-esque from these parts. My wife's friends from school are living there with kids our daughter's age. We've gotten her into a good public school, we've already found a place to live till the end of the year. There is family in Perth. And with a visa coming in by September or so, I'll be eligible for getting funding for a PhD or something like that (whereas I'd need to wait for 5 years in the UK).
To be honest, I'm pretty nervous about the isolation and cost. My wife is a little apprehensive about 'going back.' But it does seem like the more sensible option, since we'd be forcing the UK to work for us (in the same way that I think many in these forums seem to force Aus. when it might not really be a good fit). Maybe time will change my conception of what's sensible, who knows? But I have been enjoying lurking on these forums to try and get a sense for both sides of 'the fence'.. and which side the grass is greener on for the person who's not already on one of the sides.