Without a doubt clareabelle they are bad for night sweats. I have recently replaced one with a supposedly cooling, silk-topped summer-winter mattress (reversible - different construction each side) for that very reason & it's proving quite an improvement. If you google hard enough you'll find memory foam is notorious for its insulating properties. Unfortunately, some years ago I believed a salesman who insisted otherwise. Have spoken more recently to a good mattress specialist about new memory foam variants marketed as cooling & he tells these are not much better & also best avoided by ladies with thermoregulation probs! Sorry to be the bearer of bad news. I hope you manage to find a way around it.
Wx