Fly Stimulator
One can see various figures on the CAA website showing the number of PPLs etc awarded each year, and the percentage that go on to do IMC or IR afterwards, and certain conclusions can perhaps be drawn from that. I once wrote to the CAA asking for dropout rates (because figures attributed to the CAA come up in the press from time to time) but they declined.
"CAA" figures I have seen were 75% of PPLs lapsing with an average of 10 hours flown, and 93% lapsing within 2 years. These certainly tally with what I have seen myself hanging around the training scene for a few years, and the latter was confirmed to me by a busy school which has been at it for many years.
My view is that large chunks of the absolutely ancient syllabus do need a rewrite if people are to come out trained to fly with confidence. However an equally desperate need is modern aircraft and that is just not going to happen because most of the training industry is virtually bankrupt. You could do it in rare situations e.g. a well funded and well managed school in a good catchment area and with no competition.