I cant comment on a Morgan since I dont have one. But on the Lotus I found the aircon very useful, mostly in wet weather with the hood up. A small confined cockpit meant that if you got into the car with rain on your clothes the windows steamed up dreadfully and the aircon was needed to clear it.
The other use was in really hot weather when it became unpleasant to drive with the roof off. Then it was roof on and aircon.
