I need to get power, water and gas from the existing house to the other side of the new extension (3m). I'm laying 100mm of insulation then a concrete slab. Do all the services run through the insulation? There's plenty of space in the roof but that seems the long way round. Will a couple of lengths of 110mm be enough, or I've got some 80mm round conduit? There's 5 circuits, hot and cold water and gas to get across. I wasn't planning on fitting the gas and elec myself, but I also haven't found a man who can, yet so I want to keep it flexible.