The shops in Clanfield were fitted with LED lights, but I'd never got round to connecting them up. Embarassment finally kicked in.
The lights are controlled by CML Electronics MSC8 scenery decoders. These have a lighting sequence that makes the lights go on and off periodically, so the houses and shops look occupied. I've mounted the MSC8 units into the same bakelite boxes that mains power sockets use: a double wall box fits an MSC8 nicely. The boxes are munted behind the backscene, ie very near where the wires come through from the models.
To get an acceptable brightness I have added 3K9 series resistors at the MSC8 end. As far as I recall there was already a 1K resistor inside each house in series with two white LEDs; put bluntly they were too bright. Now, we get acceptable brightness with an estimated forward current of approx 1.5mA through the two series LEDs.