Fitted with a series of thin electrical wires that heat up your bed when they're plugged into your mains electricity supply, small double electric blankets can heat your bed from under the sheet or from on top.
Available in two main types, fitted under blankets and over blankets, 4' fitted under electric blanket heat the body from underneath and add extra warmth to your bedding.
A small double over blanket will warm you and your bed from the top. Generally available with heat sensitive technology, over electric blankets adjust to the temperature of the body and room while you sleep and can either be placed on top of the bed, or inserted into a duvet cover.
With the added convenience of being machine washable and tumble dry safe, a good quality small double 4' electric blanket will also help keep your bed fresh and clean.