For under bed insulation, try a couple - side by side to cover under the whole mattress if larger than a bedroll/sleeping bag - those yoga mates/camping mats. I used to use them and a scrap of carpet when sleeping on the ground when camping. I also found that wrapping myself in a queens bed size doona (a synthetic one not a feather one) - the size is almost double a single bed - would help a lot, the under as well as over. If you can get scraps of that blue house insulation paper, try some under the mattress too.