It could be that the Number Plate doodah mis-read the plate of a Ford Mondeo or something in that bad visibility and they identified it as your car.. but if it's a time and date and route that you used.. you may be buggered.
Ask for a photo so you can see if it was your car or not..
If it is you, then at least you'll have proof showing your car, time and date .. and that you were clocked at 98mph in a 30.. or something.
But say your missus was driving at the time..
But at least it makes the points/fine a little easier to bear if you have a souvenir out of it..