Guardian: Motorists already struggling with the highest ever petrol prices face increases in road tax this month that will see many buyers of new family cars paying £425 in car tax. Drivers of some two- to three-year-old petrol cars will now also have to pay significantly more to tax their car. Some luxury car buyers will pay £950. In 2008 Alistair Darling announced a radical overhaul of the vehicle excise duty regime to encourage the use of cars with low CO2 emissions. The changes came …