Should I have gone to specsavers? or is that screenshot just illegible?
You'll need to test that the monitor is not dropping frames, it's possible that it will accept an input of 120hz but that doesn't mean it's displaying them.
spec savers, plus ctrl + mouse wheel up.
its not as clear as it could be, but its just about clear enough to see the important bits
Cru is an excellent tool, I was using it to push 120Hz over single link dvi on my old lightning
May try this later see if I can turn my 120Hz into 144Hz