Lol @Sarah977. If you come to stay with me, I will do my best to make sure your room is balmy, but yes, you should probably come in the Summer!
I actually feel the cold very much. I think it is genetic. I come from a hot climate, so my body is programmed for that. I can handle heat much more than cold. I spent six months travelling around Mexico and Guatemala, got brown as a nut, and loved every moment of heat and sunshine.
You are completely right of course that it depends on what you are used to. However, Mr. Sick was from Germany, not a hot climate. It is as cold, if not colder there. He was getting up early for work so I adjusted the timer for the heating to come on well before he got up and also to come on before he got home from work. The only thing was that it was not on overnight, which is very uncommon in the UK as far as I'm aware. There is plenty of documentation to show that sleeping with central heating on is BAD for you. Also, most guests from other Western European countries have told me that it is normal to have it off there too.
I think the real difference was that this guy lived in a small, modern apartment, not a big, old house with high ceilings and big sash windows. It doesn't matter how much I have the heating on, it's never going to be as warm as that small, modern apartment.
I get what you are saying about people's immune systems etc. but this guy left with a big smile saying everything was perfect, not that he was freezing cold and feeling unwell. It was after he got home and came down with a cold that he decided it was all my fault.