I doubt that Australians or British would set up distinct communities. Of course, the majority of foreign graduates, postdoc and faculty are Chinese and Indian, but given the few full Professor positions there are, there is quite a high proportion of British and Germans, actually.
But even if 50% of all full profs would be British, it still won't numerical enough to build up a British community. Brain drain does not mean that there are thousands of people leaving a specific country, but rather that a limited number (as there are relatively few to begin with) specialists are lured out of the country. In the worst case they are the best and brightest, as the payment (at least for tenured Profs) tend to be higher than in other countries.