I'm replacing a 40-year old boiler which is situated in a room in the middle of the house. This means that the choice is limited to something that can be flued up a chimney. The best option that I've found is a Keston C36 boiler that uses ordinary 50mm plastic pipe for a flue. Does anyone have an alternative boiler, bearing in mind that it has to be flued up the chimney and that it can't be flued through a wall.