I'd go:
Joni - Can be brilliant, started out cool, got bogged down by involvement with jazz - Jazz can be cool, but is never cool for a pop star;
Blockheads - Ultra Cool with Dury, Cool making FGTH records for Trevor Horn, generally still cool unless Phil Jupitus is involved;
Suede - As cool as...
I've been over thinking this one. 'Cool' & 'Uncool' seem to be a movable feast that would allow virtually any artist to fall into either category.
If you consider that 'Uncool' is another way of saying 'Out of Fashion' the questions that seem to follow are 'Out of Fashion when?' and 'Out of...