Toby is essentially right - as long as the hours could have been logged as P1 under JAA rules, they count.
The reference as to what counts is
LASORS, Section A, Appendix B. On page 40 of LASORS (scroll, confusingly, to page 56 of the file I've linked to) you'll find a table showing how to log your time under JARs.
You will find that any time you fly with an instructor for the purpose of gaining a license or rating has to be logged as PUT, and can't be counted towards your P1 time for a JAA license (this is item G of the table I'm refering to.
However, FARs allow you to log some time towards your FAA IR without an instructor. If you've taken advantage of this rule in getting your IR, this will count as P1 - as per row A of the table in LASORS. (And if you've flown as a safety pilot for someone else, under FARs this counts as P1, but under JARs it doesn't count at all - you can put it in your logbook as "SNY" - Supernumary - but you can't count the hours towards anything at all - this is covered in either row F(iii) or row N, depending where you look for the definition of "safety pilot", but either way it turns out the same.)
Hope that clears it up!
FFF
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