Thank you FS for the link.
The frustrating thing is that the CAA (clearly deliberately) doesn't publish data on the "churn rate" in licenses. I can see they don't want to publish data on how many new PPLs chuck it in within 1,2,3 years etc because I believe that would make the PPL training business look bad and would not do GA any favours in the bigger picture, but this also makes it hard to work out figures like the original question here is asking.