I'm trying to get installed Heat Recovery Vent into a 2nd floor flat http://www.i-sells.co.uk/vent-axia-lo-carbon-tempra-selv-lt-single-room-hrv   I need a little of the harling chipped away to make the bottom of the existing core hole a little wider and then a PVC plastic face plate screwed to the wall.   The problem is that this work needs to be done at height (approx 7 meters as red circle below shows) and I'm not sure if a builder would need to erect a scaffold and p