Hi All,
I was told that my problem was caused by a pin hole in the clear coat and condensation got in due to the strange wether we had this year while it was under the cover, ie lots of rain but warm humid conditions. I had left the car covered for about 3 weeks in the summer when we had all the rain, yes there were dry days but the cover was soaking and if it had rained again while I had taken it off I didnt want to put it back on a wet car, if you know what I mean, so I left it on. This is the third year I had used a cover and had had no problems. I think it was more to do with the weather conditions.
In my opinion, for what it´s worth, I would have no hesitation in using a cover for an extended period over the
winter months as long as it was a good breathable cover, it fits properly and is well secured. But I dont think I will use it during the summer months any more, I will have to just clean it every week.
Hope this helps