whisky-dave wrote :
So it's only used when you want it, so you wouldn't need a system where if no
one is the the light goes off, which is what we were talking about in offices
and lecture rooms.

I did actually mention I used a room occupation switch, where and its
reason - I only mentioned the system I use for the outdoor lighting in
passing. You asked about the latter, I explained as you requested.

The 9w lamp costs around 11p to run for 37 days of use, by my
calculation, so hardly worth struggling in the dark or bothering to
only switch on when needed. I fitted the solar clock way back when we
had 100w of lighting there.