Thanks girls. Ended up now being able to actually make the butter icing until shortly before I was going to ice the cake anywhow. So much for forward planning lol. Have put iced cake in the fridge to keep dog away from it and butter icing had small amount of milk in it. Dog had already tried to take a swipe out of it before I iced it! Mammoth task as I had decided to do a 3D Thomas cake so had both butter and fondant icing as well as heaps of cutting and shaping to do! Not really expecting a 2 year old to appreciate it tomorrow though lol!

Thanks again for your advice :-)