Hi - just having cavity wall insulation retro fitted (spray foam wool) and the install has said they cannot do 1 wall (gable end wall) as there is some sort of partial polystyrene board already in it, but only the top 2/3 feet of the wall! its a full 2 story height wall! its part of an extension that was done year ago (before we move in, probably in late 80's or 90's. its not in the other 2 walls of the extension. if i was a suspicious person i'd say the builder stuck the boards in the top to try and fool the building inspector / owner - but its not in the other 2 walls! any ideas on how to remove, fix so the gable end wall can be retro filled?