Thanks sorry for typo. Yes you're right about electricity being less
efficient, although I'm in France and our rather new apartment block
uses electric heating only (probably cheaper than the UK: France got
loads of nuke stations). So no difference compared to gas. But the
other guys are right, most of the heat from incandescents go right to
the top of the ceiling (not many people up there).
About the better lifespan of fluorescents, I'd assume that it's more or
less exactly offset by their greater purchase cost?

Seb

PS You guys have been much more helpful than another environmental
newsgroup--don't wanna put down others but my posting on this topic
attracted a great big flamewar between a few others about being "Green
Goblins" but no useful answers.