Wow, we Australians have escaped remarkably unscathed in this thread. Didn't anybody think of Rolf Harris ? Now that would annoy the pants off anyone ..... errrr, sorry. Wrong metaphor.

Oh, and Aussie bush band singing is an acquired taste. I love it meself, but I know it would make some of you sensitive Brits come out in boils.
As for Eric Bogle, whom Jack Campin mentioned: sorry Jack, Eric doesn't come within coo-ee [ viz, a long way] of an Aussie accent. His affected twang is deliberate, and good!, comic relief.

But to put my 2 bob's worth into the argument - a couple of contenders as yet unmentioned I think: Rita and Sarah Keane ( of ethnomusicological worth only), and .... sorry to speak even more ill of the deceased ... Margaret Barry ( just torture).