under various EU directives, it is legal. however, you may have difficulty in getting the cover at a cheaper rate than in Ireland. The other EU insurers are not ejits. They know the cost of claims here and would rate you accordingly, if you could get one to quote for you.
You must be truthful. theres no point in giving a non irish address as your address, especially if you have an irish registered car. if you have a non irish registered car, then you run the risk of customs seizing it.