if they are saying u were driving car x with that reg number x, then as u weren't driving that car, u plead not guilty, as u weren't driving a car with that reg, they can't do u for driving a car u didn't drive, say u don't even know anyone with that car reg, ask what sort of car it was, and in what part of the country it is reg'd in, make them work, i got the book thrown at me once, but they couldn't prove anything so it got thrown out, that was all because they got no signiture at roadside and couldn't prove it was me, case dropped