You will get condensation inside the cover i.e. the painted part of the car that gets wet anyway but the underneath should (theoretically) remain dry and a cotton lined cover will retain moisture.
If you cover it outside one of the biggest issues is wind, if it starts flapping around in the wind it will mark your car, cotton lined or not....
What about one of the folding garages I have seen advertised around the place, you drive the nose of your car in and then it folds up and over the car...
https://www.uktoolbox.com/products/sealey-tools-vehicle-storage-shelter-medium-3400-x-1800-x-1900mm.html?F1=0&ID=511409&utm_source=GoogleBase&utm_media=Product+Search&gclid=CjwKCAjwqpP2BRBTEiwAfpiD-y4kktf1PHVFQENuWnZ0FuwFpvqEnxorJp8WyM6GyQw5LqFPIBD1gxoCMEMQAvD_BwE