We bought a Rainbow Screens cover for our Reimo pop-top. It fits well (as it should because they ask you to measure even for established pop-tops) and is good at keeping the weather out. It definately helps with the insulation, but just having the roof up makes a huge difference to the amount of heating required. We usually use an 800W oil-filled radiator when on EHU, and this struggles in cold weather with the roof up even with the wrap fitted. I’m not sure how well it would cope in the Alps in winter, so I will probably keep the roof down. Mind you, I’ve not tried it with the Webasto going yet …