Looking for some advice on how best to insulate our loft for the part which will be boarded up. Recently moved into a 1950's end of terrace and had to bin all the loft insulation due to having to treat for woodworm and to clear up after what seems to have been a mouse infestation. Wood worm treatment is done and now is time to start insulating it all over again. The joists are 80mm deep and spaced 14 inches (36 ish cm) apart. Have decided on 2 layers of This. The issue is however with the section that is going to be boarded for storage. With the joists only being 80mm deep I'm looking to use a 75mm Celotex/Kingspan PIR insulation board between the joists then board over with insulated loft boards. I need to know if this would be the best way to board the loft, or if a better option is available? Also I have seen non Brand PIR boards that come in widths small enough to fit through a loft hatch, does anyone know where online I can get these from? Thanks in advance.