Low emission cars are increasing in popularity, according to a BBC article today: http://www.bbc.co.uk/news/business-17740356.

In 2007, only one in ten new cars sold was a low emission car, producing less than 130 grammes of CO2 per kilometre. In 2011, nearly half the new cars in the UK were low emission.
These low emission cars deliver an average of 54 miles to the gallon. Of course, some are much higher.

There is a close link between reduced fuel consumption and emission reductions, and the result of this trend is a big step towards a low carbon motoring future.