You should show an insurance disc. Road tax should be on petrol (this was mooted in the 70's, but for some reason it was deemed to penalise elderly people - it didn't dawn on the powers that were that the elderly would actually gain because their consumption was small). A proportion of taxes raised should be actually spent on the roads, safety would be improved and pollution would drop substantially. Please don't expect politicians to act logically - we're a bankrupt country that can't afford to repair dangerous roads, but can afford £M150 per medal won in the olympics.
As an afterthought, another bonus is of course, that you catch foreign drivers if you tax fuel. They charge us tolls.