If I have a double storey house, would there be insulation at both the first and second storey ceilings?
It depends on what was done at the time of construction. If the building was built after the 70s, it usually has insulation on the second floor ceiling.
If you’re building or renovating a double or multi-storey house, then there may be good reason to considering insulating the mid-floor, i.e. between the ceiling of the ground floor and the floor of the second storey. The main reasons to insulate between floors is to reduce the noise transfer and heat transfer between floors.
If your home has no easily accessible attic space (i.e. cathedral ceilings), you can still insulate it with polystyrene boards.