I found some of the article familiar, some confusing (note: I'm a pom who made the reverse journey many years ago, after MHT kindly arranged to fund my passage).
Although I agree that there are many ways in which Australia lags behind Europe, in my field (I work in Local Government) it often seems the reverse is true.
As to the cultural experience, there are opportunities in both countries. Yes, from London you can get to Paris in a short time ... but from Australia you can go to many equally diverse places with relative ease. And, in many cases they're cheaper, they drive on the correct side of the road, plus (unlike Parisians) the locals will actually be polite to you.
I can't answer for what London is like now (it's a few years since I've been there), but if it's more diverse than Australia I would be very surprised - both in my workplace and around my home, I can think of at least a dozen different Asian, European and other nationalities represented.
Agree with Piers though that it is important to get out there and experience the world - whether you go from here to there or there to here, there will be new experiences and you will be the richer for it. But, be open and prepared to make adjustments - even between UK and Aus/NZ, there are cultural differences, which is one reason why so many poms fail to make a go of it here.