Allan Gould wrote:
I have been very happily using a "15W Osram Dulux EL Sensor Energy
Saver" bulb. It's a typical low-energy bulb with a sensor that will
switch on/off in dark/light conditions respectively.

CPC have them in stock. Go to http://www.cpc.co.uk and search for
LP02248 (bayonet cap) or LP02249 (edison screw). Page 1373 of their 2006
paper catalogue. £12.70+VAT

--
Adrian C