I guess I'm a bit dense, but is there a way to adjust the overall colour of an image within Qimage, in other words if the test result is a bit magenta, can I remove that or do I have to go back to Photoshop?

I've played with the Sel.Color tab, but nothing actually seems to change for me.

I know I'm doing something wrong, so can anybody help me?

PP

Sounds as though your "test result" is a print.  I have been through that with certain papers.

In the full edit try going to -3 Red and -3 Blue in the white balance.  You'll have to play to see what works.  Since there are only two colors and no sliders, you have to treat it like enlarger color printing.

I have to disagree with Fred about using saturation.  Messing with that for a color balance can cause tonal shifts in other areas.  Levels/curves is dfficult to get an overall change if that is what your problem is.

Since you have PS, I have found it easier (if it doesn't hit in QI with a slight adjustment) to go back to PS and use Image>Adjustments>Photo Filter for the appropriate overall shift.  I find 3-8% is plenty.  I just save it as xxxxxA so I still have the original.