I'm a licenced radio amateur (G4DYO) and I know that in the past such offenders have been dealt with, but I also know that the level of "policing" of the radio spectrum in the UK is considerably lower than it was 20-30 years ago. When I first obtained my licence the Post Office Radio Engineers would frequently inspect my station - on a "surprise" basis to ensure that all was well. Such inspections ceased many years ago. It was the same department which sought out and prosecuted radio spectrum abusers but I'm not sure how often this occurs nowadays, or even if the department still exists.