Thanks ed_pete. It makes sense that the double gang switch would both be double way. Like you say I now expect the issue to be with the single switch on the 2nd floor. Is it easy to tell the difference between a single and a double way switch if I were to look at it? If it is double way, is wiring it to operate that way or indeed replacing a single way switch with a double, something that's easy to do for an amateur? In other words, is it just how the internal connections of the switch are........connected, or something more involved?