Euro Truck Simulator 2 is the most realistic street driving simulator I know of, and it includes roads in the U.K. I found it good driving practice when I hadn't driven for a while (as I don't own a car).

ETS2 only comes with trucks as driveable vehicles. A lot of the skills are the same as driving normal cars, but trucks have more gears, are larger, and accelerate more slowly. Truck cabs also don't have rear-view mirrors; to look backward you have to either use side mirrors or stick your head out the window.

I have seen mods that add normal cars to drive. I downloaded one of those mods but haven't tried installing it. I'm not sure if those mods unlock the cars from the start or if you have to first save up for and buy five trucks to unlock the in-game online vehicle ordering catalog (which takes many hours of gameplay).