Its too early for people to be going to race meetings in Naas... just watched a Helicopter that looked really like the 139 go overhead very low. Its kind of blunt looking from below, has a white/gray belly, it did a 180 and seemed to be heading back towards Baldonnel. Doesnt sound anything like the current fleet of Heli's.
edit: i know there's one of these topics posted every month or so, but I wouldnt have done this unless I was at least 50% sure it was a 139, it was a white helicopter, normal tail rotor, two wings on the tail, large, and blunt. It could of course be some civilian chopper but perhaps not....