Tzymische, I was not aware that one agency was basically all there is in Ireland, nor that all the charters are with them.
That isn't the case. I'm only on the other side of the Irish Sea, and I'd never heard of CFT until today!
From looking at their website, and from what Tzymische has posted, they seem similar to BSAC, in that it is a club-based system with volunteer instructors. Scotland also has something similar, called ScotSAC.
BSAC has a presence in all parts of the UK and Ireland (and even other countries), and the likes of PADI, SSI and the techie types do as well.
I'm not aware of any Irish charters being affiliated to any agency, but I'd expect they are similar to the ones in the UK (i.e. no Divemasters, no crew setting up your kit for you, and no agency affiliation) - Tzymische will no doubt clarify.
On the subject of PADI and Ireland, I learned to dive with a PADI outfit, where I live in landlocked Manchester. The school was once a BSAC club, and back then, PADI did not really have a big UK presence. In those days, training was done in a club environment, so a novice course could take months, as pool training was confined to midweek evenings. As overseas travel became more available to average people, many people wanted to learn to dive so they could dive in the warm Mediterranean, but didn't have the time to learn in a club environment. One of the founding members saw an opportunity to offer crash courses, and people would pay to be taught when it suited them. A commercial dive school was formed and they were offering BSAC courses.
As PADI gained a bigger worldwide market share, many people wanted PADI courses, so the school began offering these as well. Generally they would still run BSAC courses for people who wanted to dive in the UK, and PADI courses for resort divers.
One day, the owner was out. His elderly dad lived with him in the flat above the shop, and was looking after the phone for him. He got a call from a chap with an Irish accent, enquiring about diving lessons. He asked him if he wanted to dive in the UK or just abroad. The caller told him he just wanted to dive abroad, so he replied, "
We'd best do you a PADI course then...", which seemed to offend the Irish caller...