I tried Reflectix and finally decided that there was virtually no improvement for any application I tried. I do have an 8 inch foam mattress that provides good insulation. Good insulation or not, the bed starts out cold. The heat does a poor job of circulating in the bed area. I have tried running a fan to move warm area over the bed. That helped a bit. The blankets have to be turned down and it takes quite a while to warm up the area and the mattress and bedding.
I recommend checking Amazon or other sources for a good, large, covered hot water bottle. The hot water bottle not only warms the bed, but the modern ones use boiling water and stay hot for many hours.