We left Weymouth heading SW, because of weather and current, passed within distant view of Guernsey, got almost to Ushant, and have just turned NW, under sail, to pass the Scillies for the open ocean.
They don't sell (apparently, after a long browse at B&Q) simple light switches.
What we call in the US a three-way switch is a 2-way switch in the UK.
You just wire two of the three terminals for simple on-off.
A US "four-way" switch is an "intermediate" switch here.
This makes sense to me.