I agree with everything except the ladder, due to the fact the regs only mention a purpose made means of access, I don't think this constitutes the requirement of a ladder. The next time I come across a building inspector Il ask him, along with getting clarification on soil stacks and air emmitance valves but that's a whole new thread lol it's interesting you mention notifiable extensions though as that was the last boiler in a loft I did no call backs............. Yet ;-)