I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For Pat(rick) Gavin M 1842 +/- 4 yrs, I found 22 rcds - too many to summarize here.
For Ann Slattery M ditto, I found 5 rcds: 1838 Limerick*, 1841 Tipperary*, 1842 Westmeath*, 1844 Cork, and 1844 Limerick. The asterisked items indicate POTENTIAL matches for the same yr/cnty. Screening these at the parish level, I found matches in the same parish, Clara Horsleap, in 1842 Westmeath. I think I may have answered this question in another of your posts.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.