The clicking noise I originally described has been resolved. It required replacing the 'stepping motors' and control unit of the HVAC. The dealer replaced under the certified warranty.
I also have an intermittent noise which seems like the one you describe - a kind of gurgling sound from the dash. This apparently has to do with condensation under some circumstances. Its described on the BMW TIS.
As I understand it, its harmless. BMW does have a kit/procedure, described on the TIS for the dealer to eliminate it. BMW also claims that it should go away in recirculate mode - haven't tested.
I first noticed this gurgling noise a few years ago after the dealer replaced the water pump. Since it is only occasional and is apparently harmless, I never bothered doing anything about it.
Good luck!