I checked this with my HV the other day. It depends on the age of the baby I think, but she advised me to stick with a vest and sleepsuit and a light blanket. She said that while we may feel hot, newborns don't have enough fat on them to keep them warm, and they don't generate any heat during the night as they don't move around in their sleep. They also lose heat quickly.
I've kept Madeline in a vest and sleepsuit, and had one layer of a celular blanket on her. She seems fine in this but I do check during the night to make sure she is not too hot. She usually kicks about if she is too hot, and then I remove the blanket.