Thanks for that tip but I've already had one re. Folding ones from Jon E that I'm following up and hope to take delivery of soon. I'll report back about it, it was just over £200 and folds up and stores very easily when not in use.
A slight divergence from this thread but I think relevant.
I had very good quality outdoor cover for my 1929 short wheelbase saloon. It was for a Smart 2 seater and fitted almost perfectly. Shape correct even down to the 'ears' for the door mirrors. A little bit wide but length spot on.
I suspect a cover for the Smart ForFour would be pretty close for a LWB car.