The ideal temperature for a house in the UK depends on various factors such as age, health, and personal preference. However, most sources agree that the ideal room temperature is between 18 to 21 degrees Celsius during winter. The World Health Organization (WHO) suggests 18 degrees Celsius as the ideal temperature for healthy and well-dressed people. The NHS recommends heating the areas of the home that are used the most, such as the living room and bedroom, to at least 18 degrees Celsius. For vulnerable people such as the elderly, the recommended room temperature is between 18 to 21 degrees Celsius. The Lullaby Trust advises heating a newborns room to 16 to 20 degrees Celsius. Its important to note that increasing the room temperature by just a few degrees can substantially increase energy bills, so its best to avoid turning up the thermostat too high.