JimM wrote:
'...I should be delighted to learn of an electronic sensor that wil
detect approaching dusk and switch a compact flourescent on for a
predetermined time (preferably not dusk to dawn)...'

Is this the sort of thing you are after

http://www.tlc-direct.co.uk/Products/STNM3000B.html



Cheaper than that in Richard Dyas at the moment.