Elywn,
Yes, I will have to check the Marriage records at the NLI the next time that I am in Dublin or try to view the local parish records. I would even suggest that my mother could have been mistaken over Johanna's name only that the marriage cert confirms that the father's name was Kirby. By the way, Philip's first wife was also Johanna Kirby who died in 1883!!! So it is probable that the 2 Johannas were related to one another, her father was Michael.
Gaffy,
I was fairly sure even before aghadowey posted (thanks for confirmation) that the Kirbys were from Pallasgrean or possibly the old parish of Kilmurry.
many thanks for your help.