Hosehead,
As has already been stated, 'Tanks' (how I dislike that word!) are built to be worn, not kept in mothballs to be brought out for special occasions only! Of course they can be worn casually, semi-formally and downright formally - why not? Take a look at my Photo Album (linked below) to see the wide variety of ways in which kilts, any kilts, can be worn.

Just one word of advice, however: please be careful about wearing patterned shirts/tops with tartan kilts. Differing patterns/tartans usually manage to shout, yell and scream at each other! Best to go for a plain shirt and ideally one whose colour matches one of the less conspicuous colours in the tartan of your kilt - in the case of your County Laois, I would select the light beige colour.

Good Luck, and