I've just removed the storage cylinder cabinet in the bathroom and I've gained an extra 1 metre square. i'm left however with a metre of unplastered area on an external (brickfaced) wall and metre of unplasted area on a studded wall. I,ve got some 10mm thick plasterboard which I was going to dot n dab on the external wall and nail to the studded wall. Is this ok or should I be using aqua board for the studded wall and bonding and finishing plaster for the external wall?