Our police are beginning to rely very heavily on camera and radar to catch fast cars, although they blitz a stretch of road from time to time.
It is wise to travel as fast as the fastest car that passes you keeping 1/4 mile distant, and if it brakes then you do the same.
I have a short stretch of two lane road between my house and the motorway and I usually get to 135 before I have to brake hard for the stop sign. My favourite part of the journey each day.
ALSO IN THE UK, IT IS ILLEGAL TO USE YOUR PHONE WHILE DRIVING, so only passengers could report you.