Lucy do you have a baby gate on their room? Or can you put one on for nights just to contain her in the room at least? We had to use a lock because Matilda thinks child gates are fun to climb over, but we lock her door after she's fallen asleep & sometimes we find her asleep on the floor later, but most of the time she calls out if she wants us. Bit easier on the brain than keeping an ear out for them wandering the house.