You could try the Celtic Choir for ideas, or my choir

Achill Choral Society, who do have a few. I know our choir lends out music "locally" sorry I don't know where you are. I am sure the librarian would send you a couple of copies for "assessment" purposes if you pick up the postage and copying charges.
Our choir seem to hate RVW arrangements, because mostly they are bloody difficult.
On a personal note, after singing folk music for 40 or so years (yes I started very early) and in the choir for the past 16 or so. My wife was involed before I was. CHOIRS should NOT be allowed anywhere near folksongs. The invariably RUIN them. But don't let that stop you. The choral listening public in most cases have no idea what the songs should sound like before that they get arranged to death and then further customized by a choral director. Or was I trying to say, it's not part of the Oral Tradition IMHO.
Keep singing anyhow :)
JohnB