Do the police have to put signs up if they have speed traps?

i was in a 40zone turning into a 60 zone about 200yards away. i speed up and there was an undercover police car at the side of the road with a speed gun. Another police car caught up with me followed by the undercover car. I am a delivery driver and i already have 3 points, another 3 points and i wil lose my license. There was no signs saying there were speed traps, im happy to pay the £60 fine but need my license i would be prepared to take a speeding course.