I have a small plate on the front of my scoob, and have been stopped 3 times in 3 years.
There is talk of numberplates being revoked, but everytime I get stopped, they ask me if I have been stopped for it before. Not sure it is being recorded. However, they always take a photo.
Latest stop (a couple of weeks ago) the PC (nice guy) said that they are clamping down on this now. Seen this on Web also.
The reason I run the plate is cause I like the look of it, and I am happy to pay the 30 quid a year for the privilege - but getting stopped more often is making me think twice.