"Dave Plowman (News)" wrote in message
...

Snag is light switches don't normally have a neutral available. The type
which is on with the light off gets the neutral via the light - since it
only takes a small current, the lightbulb looks like a short to it and
thus provides the return. I suppose you could run a small neon to earth -
since this is no worse than many SMPS do. But don't tell anyone I
suggested this.

As long as the rcd, if present, doesn't trip.