Take something warm with you
It is a good idea to keep a jumper, scarf or even a travel blanket in your hand luggage (warm socks are a win too). Even if it’s not cold when you set off, you can be sure that when it gets dark, the temperature will drop, especially if the coach has aircon. You can always take layers off! Even if you don’t get cold, you can always double up your jumper as a pillow or head rest.