This works for us along with condensation matt under mattress and a 4mm silver lined foam insulated mat under that. Bedding doesn't get wet
A hot water bottle and donna's. Bed end awning also helps.
The blue matt is a yoga matt, you can purchase off the roll at Clark Rubber. It rolls up and lives under the bench seat when not in use.
These also work a treat. The misus puts them in her jacket pockets as well to keep hands warm during the day. Ive also used 6 packs worth in the bed a couple hours before we turn in when I forgot the water bottle.