"Any" angle was a big ask, I know. Personally, I'd be happy with 90deg anti-clockwise. Currently I can only get 90deg clockwise. I raised this with Cognos and they've created an enhancement request.
With my user hat on, I can see how it would be easier to read at a more acute angle such as
45 or 60; the sort of thing you can do in Excel (much as I hate the beast, it does have good layout options). Granted it does take up more real estate. And I was also thinking that this should be EASY for non-technie authors to implement - which tends to rule out workarounds heavy on the scripting and graphics manipulation.
But I will try the suggested css option & see if that helps - thanks, guys!