Raceboy..Plod=cops!
Don't underestimate what the Police can, or cant do.. If it was your local beat bobby (cop)
he was probably just interested in your car.. ie, something different.
If however you get pulled by the Traffic boys, don't get saying that your car passed the MOT with them on! the tester could lose his licence!!! best thing to say is that you just fitted them! you'll probably get a "producer" ticket, and take your car to an MOT testing station for inspection, It'll be a brave tester that says there safe for the road! especially as the police are involved

The police could also use manufacturer's fitting specifications as evidence, I doubt that you would come out on top!
By the way, this subject was covered a few weeks back, on page 5, check it out
Tom