As usual, I get in on the tail-end of a juicy conversation...so I'll just add my 2 kopeks worth.

As to the British vs. American English debate, I get bombarded almost daily with this issue, as I'm an American teaching English here in Madrid, where overwhelmingly most of the English teachers are British.

Funny thing...MANY Spanish people, especially business people, specifically request American teachers...in order to pick up the American accent, phrasal verbs (a lot of differences), idioms, etc. Less and less requests are coming for British teachers at our school.

Also, most of my students have told me repeatedly that it is much easier for them to understand my American accent (which is clean and flat, coming from the Midwest), than it is to understand British accents. In fact, I've known occasions when students will reject their British teacher, because they simply cannot understand their British teacher, but can more easily understand an American teacher.

As to Aussies, of which we have a lot teaching in our school...Australian English may have its roots in British English...but honestly, I think Aussie English is much closer to American, albeit the accent and the obvious vocab differences. And most students I've observed have a far easier and more productive time with their Aussie teachers, over the British counterparts. I certainly have a much easier time understanding Aussie English than British English. Countless times I've had to ask a Brit to repeat something because of the bloody strong accent...almost never a problem with an Aussie.