I hope everything goes well for you in June! I'm positive that it will, but of course keeping your options open is always a good idea.
First of all I'll say, as someone who's experienced this, that if things *don't* go quite as well as you're hoping, don't give up on Uni. I know that 6th years can't wait to get out of school and think that another year is an eternity, but the year I repeated the Leaving made a huge difference to me, and was a really positive experience. The year flew by, helped me to decide what I really wanted to do and, best of all, at the end I got my first CAO choice.
Anyway, the reason I'm saying all that is that to practice as an architect you have to have an architectural qualification. Once you graduate from your degree, you can become an associate member of the RIAI, and after two years' experience you can take the professional competence exam which qualifies you to become a full member.
There can be other ways into architecture though. Have you applied for any architectural technician courses? A qualification like that could be a foot in the door of an architectural firm. But still, I'm not sure if, even with years of expericence in a firm, you'd ever be able to take the RIAI exams and practice as an architect yourself. (Anyone out there know the rule on this?) And working as a technician may not be what you want, since it involves putting other people's ideas on paper rather than your own. But maybe doing a degree as a mature student (which is only age 23, by the way, so not actually *that* mature) after a few years working in a firm would be a way to go.
Then of course there's the option of entering a different sphere of building design... like interior design? I know a lot of people think it's faffy, but the profession is really called interior architecture these days, and many architectural firms have an in-house designer. Even if you're working in a interior design rather than an architectural firm, there's no reason you couldn't specialise in working closely with architects from the early stages of the design work. There's more to interior design than picking out wallpaper (and what Laurence Llwellyn Bowen does has very little to do with reality)... you can be far more involved in designing the interior space itself, and working with light and form...
Then there's landscape architecture (same thing applies as with interior design... it's not just sticking a few plants in the ground). I'm sure there are loads more ways to go - I once knew an artist who specialised in creating stained-glass windows (which again involved working closely with architects). Or maybe if it's design in general rather than building forms you're interested in, you could think about graphic design?
One more thing to consider, though the costs might be prohibitive, is to study abroad.
Having said *alllll* that, I'm absolutely no expert on this - you should talk to the guidance counsellor in your school, or maybe give DIT a ring to see if there's a round-about way into their degree programme (a lot of students in DIT start off with diploma courses and continue into a degree, though I don't know if that works with architecture).
I went into such depth in this post because is not just aimed at you, but anyone who might have a similar question... my primary piece of advice, again *just in case* (!!) the old LC doesn't work out the best this year, is to think seriously about repeating. One year is *nothing*, especially when you consider the rest of your life, and being happy & fulfilled in your career.
But now forget everything I've written because you'll be fine!!!