What led you to believe it was a 40 mph speed limit?
What type of road is it, how wide, where is it etc?
The default situation is that as a suburban road it is a 30 mph limit unless indicated otherwise.
Why do you believe it is 40 mph?
I will check the film , not having too much luck so far
You will get some points 3-5 and a fine.
A road awareness course is unlikely on a minor speeding charge.
30 mph is the default speed for suburban roads so it is 30 mph unless it says otherwise. If you plead not guilty and are then found guilty you will get more points and a higher fine so I would plead guilty.