I was reading the new WMB and they had a panel with a discussion on the validity of wearing helmets while cycling. Despite the myth that not wearing a helmet on road is safer (as in it would not cause an accident), if and when an accident happens you will be sorry if you are not wearing one, especially if your head gets knocked on the kerb. I understand (slightly) if people do not want to wear a helmet because they believe in the myth, but people who do not wear one because "it looks ugly" or "it doesn't look cool" are, well, idiots.
I myself am a slight hypocrite on this issue. 90% of the time I wear one, but if I wanted to nip over to the store less than a mile away I usually don't wear one (though I am mending my ways now). However I always wear a helmet when I go off-road. It just makes sense. But with people happy slapping cyclists I believe it is time that anti-helmet cyclists should rethink their attitude. Helmets are not what they used to be. Modern cycling helmets are not the hideous creatures they once were just five years ago. They look great (even cool), are cheap (Giro has models from £30), have proper ventilation, fits great and some models even protects your hair from nasty bugs. Many manufacturers also have free replacement policies. Trek for example (well on the model I own anyway) would send a (free) replacement helmet if a Trek helmet is involved in a crash. A similar policy exists for Met.
Another thing - cycling lanes are useless, at least those in London. Especially those that are only three feet wide and share the same lane as buses. A safer way to cycling on-road is to cycle in the middle of the lane in front of a car so the driver can see you. This tends to work in Central London as cars barely go quicker than a competent cyclist anyway.