I also bought some more styrene to use on the top of the 3 story Game Craft building. I need some sort of roof access item or chimney up there to use to remove the roof. Have not figured that part out yet. TheScene.co.uk has some interesting looking stuff. These look ideal if they were not out of stock. (http://thesceneuk.com/shop/building-accessories/mv001/)
I am debating on balconies to add to the back of the 3 story one. We shall see what happens.