I believe the allowance is 10% - so, in a 30 MPH zone, anything over 33 is an offence. I was done for 35MPH and did the course. It's only half a day so, if you could manage that, it will save you the three points. There is some argument about whether or not you have to advise your insurer. At the time I did the course (2 yrs ago) we were told that they must know if you collect points, but not if you attend a course.
"....its the points on my licence i am not happy about"
Then do the course. I would not bother trying to argue with the speed camera (if that's how you were caught) because you will not have grounds on which to rely. You were travelling in excess of the limit.
i was speaking to a friend few days ago who had been on a speed awareness course,the ex police traffic officer running the course advised everyone not to inform their insurance company of the course as their premiums are likely to increase and its not a legal obligation,i thought he was having me on but having read your link, clearly hes not
I can't imagine 3 points making much difference to your insurance if any.
You should take the course if you can but you have explained otherwise so just pay the fine and consider yourself lucky it is the only one you have ever had.