Thanks for the replies folks. Am leaning towards buying a decent carport, or even building my own. Have pretty well dismissed a car cover, because living in the sticks, every time you take the car out at this time of year it comes back filthy, and as others have said a cover will be like a wire brush.
Any recommendations for carports as it seems like a minefield, with some of the cheaper options looking better than the more expensive. Some seem to have very narrow openings.