Airmagnet you original thoughts are correct.
You have 36 months to have a CPL and or Instrument Rating issued/added to your JAA/EASA licence.
Once you have that in place exam credit remains valid for seven years from your last instrument rating renewal for the issue of an ATPL licence.
A "foreign" IR just reduces the training hours requirements for the issue of the IR.
So if you don't gain a JAA/EASA Instrument Rating in the next 12 months you will have to do all 14 exams again if you want an ATPL issued or the IR exams to put an IR on you JAA/EASA Licence.
So if you want to fly in Europe, Do the IR.
W1