In our kitchen, there are four electrical things all together.
Dual 13A sockets, and two switches below, one with a neon and one just plain.
Fine, except I can't work out at the moment what the second switch is for.
One socket does the wall wart for the water softener.
One socket has the 13A plug for the lighters for the gas hob.
The switch with the neon is for the cooker extractor fan (which needs sorting).
This leaves me with one wall switch and no obvious appliance near it. It is on the outside wall but there isn't anything outside near it either.
I thought I had sussed it when I remembered the under unit blowers for the central heating but no, it doesn't do those either.
I am now wondering if there was an extra switch installed which was never used (e.g. for the water softener which is on the wall wart) or if there is some other device in the kitchen which is a long way away from the switch.
Next stage would be to take the face plate off and see if there was anything connected (that is, wires in and wires out).
Remind me to label up all the switches in future just in case I have forgotten what they are for 5 years later.
Cheers
Dave R
P.S. just tracked it down to the extractor fan in the ceiling (separate from the extractor fan over the hob).