No matter what posters above have said, you'll never be free of slugs and snails in Ireland. Can I ask why they bother you so much? Do you have herbaceous perennials that are being eaten, or is your garden entirely in lawn? If just lawn, I'd ask whether it's worth the hassle to fight a battle you're never going to win - least of all with poisonous chemicals or slug pellets (btw those poisonous chemicals can include garlic as suggested by one poster - it is poisonous to dogs and extremely poisonous to cats).
Life's too short to get so worked up about a fact of nature - you'll never win - at best you'll reduce numbers somewhat, at worst you'll end up poisoning your land and local wildlife.