Night-scented stock - if you interplant it with Brompton Stock you get a nice display *and* scent at dusk.

Freesias - though they need a greenhouse in Ireland.

Violets, of course.

Mignonette - never succeeded in growing it, but the scent is gorgeous.

Old roses: Roserie de l'Haye, Hansa, etc. You can even make rose-petal-scented ice cream if you don't spray them with poison.

Sweet rocket, which grows wild all around the west coast of Ireland, having escaped from gardens - with its pale pink and violet and white flowers and exotic scent.