my understanding is that while you may not need to reach the minimum requirements for certain courses as a mature student you will/should have sat your leaving certificate for most of the ITs and universities and if not explicitly stated, you stand a better chance of gaining entry if you have.
Check directly with the ITs/univ you are interested in as they may have different age limits for entry for mature students and different requirements re leaving certificate…also some courses require you to sit an entrance/aptitude exam. Work/life experience is also taken into account.
remember universities only reserve a certain number of places for mature students..so it is competitive also.
private colleges of course will be different..
Aphra.