Get a dirty oil burner, 40 to the gallon minimum in a decent sized one, upto 70mpg on the motorway... if you still can't afford to run that, then the job isnt economically viable.
I blitz through £80 a week, and not a penny is ever used for work. I have a thirsty car, and enjoy driving it a lot (and enjoy going on missions to Wales etc when one is bored), the cost does not bother me, because when I come to my senses or I run low on cash, whichever comes first, ill get an oil burner haha.
If im still skint after that, ill get meself a push bike and problem solved.
Tax is going to stay, no amount of moaning is going to change it, just pay the price at the pump and forget about it. They cant ever afford to remove the tax now, if anything, the tax will increase (both VAT on the fuel and fuel duty).
Expect to be paying £1.50 a litre next year, oh the joys, if thats too high, plenty of time to change your lifestyle/car.