Yes there does seem to be a nice little monopoly going on there. I did look for others but didn't have alot of luck and in the end decided am going to do them myself. (Flower arranging course starts in January!)
However there are a couple of places in Portlaoise town and also theres lots in Kilkenny City, both of which are only about half an hour away from Durrow so am sure if you talked to some of those florists they'd do it, or at least so you can get some comparable quotes.
Failing that ask the priest or sacristin in your church who they use, I am not using Ballcolla church but I asked in my church and they recommended the Durrow guy!