Had a go at making some thermal sheets myself using the silver stuff you stick behind radiators its like a foil covered bubble wrap and is very strong, cost me £28 for 2 rolls and a reel of metal foil tape, looks ok but it don't fold up very small......managed to make a screen cover too.
i'm not fussed if it looks gash if it's warmer inside although i usually shut the top at night anyway but i thought i would try it....and jazz hands, hadn't noticed that...i'll try harder next time!
Screen rubbers Custom and Commercial do some excellent fitting german quality ones...dont forget VWH give us a 5% forum discount (they do have a 10% discount on spends over £100 at the moment) or put a list together and see what Bigrich at CoolairVW can do for you!