There's loads that are good actually. You've obviously just heard some mainstream without digging past that.

And Dizee Rascal is very good for what he is.

Furthermore, the Aussie accent is just as funky, if not more than the UK one. I've heard some UK ones which are plain and don't reveal the 'UK-Jamaica' roots too much. But they're not pretending to be something they're not (American).

Oh, but yes, the accent is the problem. Which goes along with the perception of the UK of people abraod (especially Americans).

But to say 'they're not good' is kind of ignorant. And narrow minded. One may not find an artist their taste, but should still be able to appreciate what that person is doing. His/her talent.