http://news.bbc.co.uk/1/hi/uk/8367933.stm
"Energy Bulbs get dimmer" - Energy-efficient light bulbs lose on average 22% of their brightness over their lifetime, a study has found. In some cases they emit just 60% as much light as traditional models which are being phased out of shops, it says. bulbs did not live up to what they delivered in terms of people's perceptions of light. Traditional bulbs lose no more than 7% of their brightness by the time they burn out - equivalent to about 2,000 hours from first use. But the new energy-saving models, known as compact fluorescent bulbs, use up to 80% less electricity than traditional bulbs and could save up to £37 a year on energy bills...

Yep I think we know that, which is why, when we're down in England I buy a stack of energy-efficient bulbs from Morison's Supermarket giving out 150w but only using 30w) - not sure if Morrisons in Alness / Inverness sell 'em.. but it's the only place I've found so far.. excellent brightness too- these 100w; using 20w are pretty useless....