On Thursday, 22 August 2019 19:16:05 UTC+1, Chris Green wrote:
Can one get 'indicator' lamps as stand-alone accessories?

Gridswitch plate with a neon module.

The third option seems most "easy to use and find" but is it actually
OK? Can one get switches which are particularly suitable for
damp[ish] locations?

You can but they tend to be a bit horticultural :-)

I would probably go for a pull switch with a separate indicating module outside the room door, if leaving the thing on and forgetting it is an issue. Or even a runback timer switch so it runs for eg 2 hours to warm the room / dry the towels, then turns off.

Owain