I live about two miles from the shores of Lake Ontario, and it has been around zero and below quite a few times now. But, I live in a condo facing south; therefore, on a sunny day we get the sun pouring in through rather large windows, we are surrounded by other apartments and a heated hallway, and the insulation requirements for buildings over here are a lot higher (I would think) over here than in the UK. Believe or not, we very seldom need the heat on all Winter!