@Jennifer1955 A lot of people have safety concerns about electric blankets, heating pads, and space heaters, although these are much safer than they used to be. Most guests are going to prefer to use central heating to keep the room at a desirable temperature rather than spot heating, because let's face it - they are on holiday, and they don't have to pay your energy bill.
It's OK to place limitations on heating usage, but they should be disclosed in the listing. Providing lower-impact alternatives for heating is a nice option for guests who are more environmentally conscious or who prefer cooler temperatures. Also, any improvement that can be made to the home's insulation before winter begins is money well spent.