The number of participants in a diversionary course in the last five years is published by the National Driver Offender Retraining Scheme (NDORS). Their website gives the details as follows:
We have no record of how many participants have since reoffended. However, the Department for Transport, in conjunction with the Road Safety Trust, has commissioned an evaluation of the NDORS speed awareness course, which is the most commonly awarded diversionary course. This evaluation will look at a number of aspects of the speed awareness course, including the impact of the courses on reoffending rates.