Interesting. I wonder if this has been in a state of flux recently. I could swear blindly I have been told by several JAA ATPL and PPL/IR candidates, over the past 1-2 years, that an ATP sits 14 exams and the PPL sits about 10. There was also a period of time, early in JAA, when no separate PPL syllabus existed.
Anyway, the key point remains: the JAA IR is a huge undertaking. The FAA IR is very significantly easier on the ground school, and probably similar on the flying difficulty (some say it's harder; I certainly found it very hard).