I am in the process of decorating my lounge and whilst i was stripping the wallpaper around the window it wasn't just the wallpaper that came away. All the plaster fell off and beneath it was, well i think it was crumbled plaster sopping wet. How to i fix this, do i need to put sealant between the window and brick?? What do i fill the big hole with between the damp course and internal wall it looks like rubble has been shoved inside it? The seal on the outside looks ok so i don't understand how this has happened and i have no idea what to do and would be grateful if someone could give me a little advice on how to fix.