Hello, my daughter is 19 months old and want to try her with a duvet soon. We introduced a pillow a month ago and she has been loving it. Which tog should i be purchasing? Have done a bit of online research and saw some people saying they purchased a 4 tog and used this all year round and dressed their child appropriately? Or do I need a thicker one for winter and lighter duvet for summer? Her room is always around 20 degrees as our new build house generally keeps quite warm but we use the appropriate tog sleeping bag at the moment. Thanks! :)