Yay, I'm third. Or sixth. (Do Yanks differentiate between British and English?)
I've never met an Australian man, but a Kiwi I worked with for a couple of years was never known to be single, so I guess there's something to it. He wasn't my type*.
Speaking personally, I take sexiness on a case-by-case basis.
Of the three women I have been erotically intimate with, the physically sexiest one is a Brit, and currently unobtainable (she is planning to marry her current girlfriend), but the most sexually adventurous/exciting one is American (unobtainable purely in the geographical sense).
*Odd thought - I consider myself mostly straight, yet I seem to have a male "type" as much as I have a female "type".