Personally, I've never heard of an employer taking an action against an employee for not working out a notice period. I'm not saying it has never happened, mind you.
Having said that, it is not a good idea to leave any employer on bad terms. Ireland is just too small a world to burn your bridges. I was on 3 months notice with one employer years ago - I got out by mutual agreement on 6 weeks notice, having closed off on all work in progress. Like most things, it is probably a matter of negotiation.