Police cannot win nowadays. If they ticket people they are moaned at for having nothing better to do (despite it being there job) And if they ignore it, then it looks bad, and people start moaning that the police don't give the service the person expects.
If you run a modified number plate, no matter how minor it is, then you need to expect to one day be pulled over, Police do have powers of discretion with motoring offences, but I have seen people continually take the pi$$ until a fine is handed to them, that is the only way to teach people, as education doesn't work most of the time, and then it is a waste of mine and your time.