>>>I should point out that i would be intending to use the Licence outside of the US(actually, in Ireland hopefully) - would this make the age limit void??
Up until about 5 years ago, I was a designated examiner for the ADX ticket here in the States, so we'll see how good my memory is... ;_
As others have said, if you're less than 23, once you complete the course and take the USS FAA exam, you will get a letter of competency, which you exchange for the license when you turn 23.
As far as "using" the license, the FAA probably doesn't consider the license to exist until you turn 23, so if the FAA license is a requirement of your employer (US, Iceland, or anywhere else) even though you're only working as an "assistant" you may have a problem until you hit 23. Nest to check out the specific requirments of your employer, and confirmation from FAA that you can't excercise the license until you phuiscally have it.
Cheers....