You make a very good point Josh.
I would say that Australian Indian restaurants typically provide "traditional authentic Indian" cuisine. I understand that "Butter chicken" (i.e. murgh makhani) is one such "traditional authentic Indian" dish. I see it is becoming more commonplace in Britain too. It would have been largely unheard of, ten years, or so, ago, I think; with the "traditional British" interpretation of the dish being Chicken Tikka Masala?
Australian Indian restaurants seem to be generally run and owned by Indians, rather than Bangladeshis. It seems to me that "regional variations" depend as much on (if not more on) the origin, background and experience of the chefs and owners than on the geographical location of the restaurant.
It also seems to me that, nowadays, British Indian restaurants are more and more diverse (in terms of the origins of their owners and chefs) and this seems to be reflected in their menus and cooking styles (e.g. the Ashoka with, what I assume to be, a more traditional authentic Indian cooking style and menu). This must be a good thing (i.e. the diversity) since it is what brought us "curries" in the first place!
I still find that the better Indian restaurants in Australia provide an enjoyable curry, albeit not typically BIR. I actually enjoy their buffets (which are commonplace here too)...mostly cos you can eat as much as you like! ;D