OK, so on my 2010 elegance (with Rhapsody head unit)I have 3.5mm Aux jack socket in armrest but can't select aux on screen. When I press the media button, aux appears on the RHS of the screen but it is "greyed out" and not selectable.

I've tried plugging a live (DAB radio) into the socket to see if that brings the button to life but nada.

Am Imissing a trick?

Not familiar with the Rhapsody HU, but is there an setup button, where you might be able to activate the AUX function? I know on the Bolero model that this is the case. There's a tickbox which has the same effect as you describe, with the AUX option being greyed out.