The only study materials i know of specific to ireland are on the irts practice cd sold on the irts website.
The owner does allow copying the material so if you have broadband and a torrent client such as transmission or utorrent I can send you a private torrent of the cd. and other pdf's i have collected from comreg.
Download Examination Files
There is a canadian study site also that i cannot find that is excellent that i used.
I used this site
HamTests - Amateur Radio (Ham Radio) Exam Training
You can use practice tests from any country in IARU region 1. UK is fairly similar. I do not recommend the usa advanced tests as there are large sections on transistor logic and imperial smith charts.
Stay with countries within the metric system. I do not recommend the arrl handbook because of this. The RSGB(radio society of great britain) handbook is an excellent guide for looking up the meaning of any term in a practice exam, but is not necessary to pass.
Wikipedia.org is as good a resource as any for the explanation of terms(not to forget google)
Here is the syllabus which is the only study guide you need heed. The irts cd is out of date and leaves out important legal sections on the comreg.ie website(which you cannot pass without) and misses sections such as impedance transformation through coax and leaves in irrelevant things you won't be tested on.
http://www.irts.ie/downloads/syllabus-2013.pdf
IRTS – Amateur Radio in Ireland, Irish Radio Transmitters Society
IRTS – Amateur Radio in Ireland, Radio Theory Links
IRTS – Amateur Radio in Ireland, Details of the next Theory Exam
IRTS – Amateur Radio in Ireland, downloads of files relevant to amateur radio
Do not get caught up in learning maths for the tests.I was told you won't need a calculator for the exam when I went in. The hardest I had to do was ohms law.
It is important that you learn bandplans and country calls. They are often over looked and will be tested on.