seaching grtgrandparent on grandmother's side

Hi,

I have A copy of my Great Grandparents (mother's side) hand writen
marriage certificate. Their names are John Leary and Mary Caul it states
they where married on 25 November 1880 at parachial church of
Clongeen Diocese Ferns (spelling may be incorrect)

I have also purchased another marriage certificate from the General Registry
Office and this has now confused me as the marriage date and the witness's
are the same on both certificates.

The GRO marriage certificate says the marriage was in Chapel of
Cullenstown and also that they lived in a place called Foulkesmill.
It also states on this certificate that their Fathers as
Patrick Leary and Michael Call ???   

I was hoping somebody could help me with some info as I have hit a brick wall
trying to find or make a connection with my Great Grandparents and my Great
Great Grandparents (on Mothers Side)

I have been on a few Geneology sites but they have not updated before 1848
and I understand that the BMD documments were destroyed in 1922.

My Great Grandparents (mother's side) came to Liverpool England about 1880 after their
marriage and their first child as far as I know his name was Patrick born in
1882

If you can be of any help or have any info it would be greatly appreciated.

Kind Regards

Jim
(James Bergin)