Andrew Gabriel wrote:

BTW, a 20W low energy lamp is quite bright for an outdoor lamp.
Do make sure it doesn't disturb neighbours or dazzle highway users.

I agree, which is why I was so intent on using the lowest wattage bulb
possible, and consequently so limited a choice of switches.

If only some of my neighbours were quite so considerate. It's like
Blackpool illuminations round our places these days.