Hi David, I've bought chemicals from both O'Leary's Camera World on Oliver Plunkett Street and from Barker Photographic (out near the Magic roundabout aka the Kinsale Road roundabout). They are both very friendly and helpful. If I need something more adventurous I order it from the UK (either retrophotographic or silverprint) they are reasonably cheap even with the delivery charge (especially now the pound is so weak). I develop my own b&w films so haven't tried anyone local for that.
Hopefully we'll ge to meet when you are here.