Thanks wfaulk, I had a quick look at those options but I don't know where to start since I'm not getting any debug messages in the console from most of the buttons.

My Multimeter has a 'MIN' mode that I was using which holds the minimum value it sees. I was using that, but I still think it doesn't have fast enough reactions to give a reading that I have confidence in. Every time I press the button I would see its little fast reacting LCD bar move but it would only give me a readout around one in ten presses. The Vol+ and Vol- readings are dead on though, every time they give exactly that reading (no need for the minimum function, just hold the button).

Oh yeah I tried my sisters PCATS tuner (just looked for button codes on the screen, no console), but no joy with that one either. Both tuners work perfectly for Radio.