Joe Offer: If you search for "Irish Wedding Song" at AMG/All Music Guide, you'll see it's attributed to someone named "Betteridge."

If you look at Ian Betteridge's web site (He's an Australian country music singer-songwriter.), you'll see that he claims credit for a popular song called "The Wedding Song." (I'm pretty sure it's the same song and it acquired the title "The Irish Wedding Song" through the folk process. He also says it was used in the Hollywood movie "Blown Away", but I couldn't find any confirmation of this at my favorite movie site, The Internet Movie Database (IMDb).

There's a midi on this page, but I think the text there has some errors. Click to play.

I concur with the sentiments expressed on this page.