I used to think of inquire as the USn/Canadian spelling and enquire as the UK spelling. I also sort of assumed that Australasians followed the UK spelling, as is often the case with spelling (and obscenities ).

Having just done a quick 'n dirty search on the BBC, it looks like it holds true that Brits much prefer the "e" at the front. But sounds like I'm wrong about Australasians following suit. Interesting.