Halion Sonice SE - can't assign external controls

I’m running Cubase 7.5 on PC, with an Oxygen 3 midi keyboard via USB.
I have watched the tutorial on how to assign the knobs on the external keyboard to particular audio or synth controls within Cubase (ie reverbs), but cannot get this to work with Audio track plug-ins.

If I select any sound within HSSE and go into the edit panel, it has already assigned the controls on screen to the knobs on my keyboard (and in no particular or logical sequence either!).

If I then add a plug-in (Reverb for this example) to my Quick controls on an AUDIO track and click ‘Learn’ - as soon as I move the knob on the keyboard, Reverb is replaced (in my Quick control list) with the name of the setting that the knob is assigned to in HSSE - which is on an INSTRUMENT track.

If I also try going into the Remote Control Editor for a particular audio plug-in, the Learn function does nothing here either.

I’m possibly overlooking something very basic, but can’t figure it out.

I simply want to be able to assign a knob on the external keyboard to any given control within a midi or Audio editor\plug-in. I’m also assuming you can assign the same knob to a different control per track?

It would also be good to know how I make the HSSE forget all of the control assignments for a particular sound, leaving me free to just assign the ones I want to remote control.

Any advice would be great!