LO is 7 weeks and I have him in his sleepsuit and a sleep bag that's 2 tog I think, and then if we turn the heating off for the night I usually still have a blanket near and around and at night feedings I'll check if he needs it. He also has a light sleep bag (Grosnug) and I have a thick blanket with that.
My lb has a vest body suit and a grow bag with a blanket on top but we don't have the heating on during the night be he seems fine and cosy but he hates getting to hot.