So I've done some research and it turns out I'm a retard that's been sucked in by American TV shows - private citizens 'pressing charges' isn't a thing anywhere. And it doesn't matter because it looks like they are going to charge McGregor anyway.
Yeah press charges is the wrong term, no victim co-operation no charge.
Looks like the old boy got paid and the gardai slapped McGregor with a minor assault charge though, well played.
Coked up little monkey apparantly jumped in his taxi afterwards as well.