car covers are a bit of an 'area'...
Personally, I have spent £400, £250, £80 and then £23 (4 times).
I found no difference between the £80 and the £23 one, and I just accept now that they last 7 months, and then they need replaced.
So I spend £23 every 7 months on this-
It remains watertight during that time, and keeps the UV off the plastics and rubber, and it's probably a good idea to replace it anyway; as the internal soft-shell layer will be filling all the time with Microparticles; leading to microswirls in your paintwork.
This size I've quoted will be too big for a Cinq, sorry; get the smaller one