I reckon that's a pretty good list, I'm not shocked that any of them are in the top 20, but I am a bit shocked at some of artists' positions - e.g. I expected Nelly Furtado and Beyonce to be higher, with Lily Allen and Will Young lower perhaps.
Still, well done to all of them.
EDIT: I'd also like to add that I don't normally tend to judge solo artists according to their personalities; for me it's always been about their music, since that's what we're meant to be judging them on anyway. And of course peoples' opinions differ on the topic of music, which is how it's meant to be.