Downward said:
35 Million Vehicles
£200 year Tax average each Vehicle
£500 VAT/Fuel Duty per Vehicle
£10 Insurance
Easily a Minimum of £2.5 Billion per year.
Indeed, we can easily get the exact figure, which is significantly greater than that, but I'd certainly agree that fuel and vehicle taxes raise a great deal of money for the government. And this does affect transport decision making, but you need to know a bit about transport appraisal to know how.
But you didn't mention speeding fines did you? By comparison, they scarcely count do they? If they really were for raising revenue they'd be a pretty useless way of doing it- difficult and expensive to collect, constant complaints in the right wing press etc etc. but then they aren't taxes are they, as well you know.
edit: here's chart of tax revenue. Spot the speeding fines...