Thanks F1geek, that worked. I did it in stages, restart/soft reset of the infotainment system, then went through the menus to do the factory resets. Neither worked, at least as far as I could tell. In the time it took to go through all the menus and return all the settings to the way I like them (5-10mins), no heat was coming from the vents (fan on auto, temp set to 22*C, outside temp 0*C).
Ah well, it was a nice idea. I guess the next "reset" step would be to do a hard reset and disconnect the 12v battery, but I don't have on hand the radio security code(s). Will probably wait until the new year cuz a cold car is better than no car!