the BBC site Janice in NJ mentioned is worth a look at. From that site here are the verses to the same air as The Patriot Game, which is also featured. I heard the Loyalist version in Belfast some years ago, so I think it was popular with that section of the community.

Come all ye Young Protestants.
Come all ye young Protestants and list while I sing
For the love of old Ulster is a wonderful thing
We'll fight to defend it with tooth and with nail
And we will make certain that truth will prevail

Around 1690 at a place called the Boyne
Our forefathers gathered with William to join
God's blessing was on them as they entered the fray
And it's due to those heroes we're freemen today