I've got a MY22 Plus Four, and I don't have a garage, and it stays out on my drive at all times.
I've put in a couple of security locking bollards, and I've got some cameras outside too.
I spent some time looking at different makes and types of covers. They need to be breathable (this is really important), multi layer, a good fit (so that it doesn't chaff with the wind), and not black (keeps heat down in the sun). The one I went for was Stormshield + Outdoor from Specialised Covers and they will have one patterned for a Morgan Plus Four.
With practice, the cover comes on and off in a 3 or 4 minutes, and I've got a large garden weatherproof box next to the car that will take the cover when its off.
I use the cover all year round, except maybe when the weather is very fine and I'll be using the car the next day. (I also think it keeps "nosey eyes" away from it too!). When the weather get colder I run a 40W tubular heater inside the footwell.
The car does get used in the winter too, if the weather is OK - the heater is great for this and the heated seats could fry an egg if you keep them on high!
The other thing I did was to get a top of the range Titan ceramic finish on the car to help protect the paint from 'cover rash' - so far after two years, I haven't found any marks on the paint at all. It also helps if you don't put the cover on if the car is dirty!!
