Two contributors have said that they are waiting for the NPPL because they cannot achieve a JAA PPL on medical grounds - hearing or eyesight.
I have been to a number of AME's in recent years and, for the last two years, have passed with no hearing test and the eyesight test has been no more than reading the 7th line( I think) on the chart with my normal glasses.
I discussed the NPPL with my AME and he thought that, in most respects, the test and the cost of a standard PPL test should be similar to that for the HGV test. Based on my personal experience, which may not be typical, you are more likely to get a realistic medical test and cost from an AME who only does Class 2 medicals. This implies that some interpretation of the medical requirements is left to individual examiners. The simplistic judgement that "you are either fit to fly or not" is not helpful.
If there are any AME's on Pprune who can help it might be interesting to hear from them.