Times (UK): Families willing to exchange their petrol or diesel car for one that plugs into the mains are being sought to take part in a Government trial of electric vehicles. They will have to be prepared to run the risk that the car’s battery will run flat during a journey and then take several hours to recharge. In return, they will enjoy running costs of about 2p a mile, discounts on congestion charges and the satisfaction of knowing that their electric cars will be emitting less than …