So what proportion of road building costs should cyclists bear? If I were to hazard a rough guess as to the percentage of new roads built to cope with the increase in bicycle traffic, I think it would be a pretty "round" number...

100% sounds efficient, but if you're set on electric heating then it's pretty lousy compared to an electric heat-pump. For example, I have an aircon at home that runs at about 400-500% efficiency for heating - not unusual these days. Admittedly, though, it's not so easy to fit as a light bulb, and not so bright either!

They'll never do that, though - their pricing structure is very successful for them in breaking the mental link between what you pay and what you get, as evidenced by the fact that people talk about their "free minutes" without mentioning the huge monthly bill!