Thanks for the reply, we only moved house last week so it's been bedlam this week!
As soon as I get a chance I'll get the photos of the switches and post them.
My house has a landing light and a stairway light.
At the foot of the stairs is a 1 way switch that controls the landing light only.
At the top of the stairs there is a 2 way switch. SW1 controls the stairway light and SW2 controls the landing light.
So, the landing light can be turned on...