It's not as daft as it sounds! We're having a conservatory put onto the back of the house next month. Dwarf walls will be built on two sides of the base, the house itself will be the third wall, but the fourth wall is the existing garden wall (pictured below). So, I need to understand how best to make this wall insulated in some way. Ordinarily I'd simply add the appropriate damp proof, insulation, then plaster board on top and plaster to finish. The complication in this scenario is that I don't have that depth to work with. As shown in the pictures below, there's only about 30mm before any extra thickness added to the wall would start to encroach over the doorway. As it's a double thickness wall, could I remove the inner layer of bricks, giving me an extra 100mm to work with, then replace this with damp proof, insulation boards and finish to plaster?