The National ACPO guidelines for Speed Awareness Courses is 10% + 9mph. The minimum threshohld for all enforcement is 10% + 1mph.
Therefore in a 30 limit, under 34mph is ignored. 35 - 42mph gets you the course (no fine, no points, no conviction) but you have to admit liability at the first opportunity (and no previous course within last 3 years).
These are national guidelines, published by some forces but accepted by all of them. If you have had tickets below these guidelines you can contact the force and get them discontinued.
