Kind of an aside, but my wife is a celiac and I was curious about this myself.
I was looking around and a few websites claim that Ireland has some of the highest rates of Celiacs in the world.
My wife traveled to Italy pretty recently and said most places were pretty aware, and also that grocery stores had lots of stuff.
This Gluten Free Mom blog has guides to traveling in Paris, London, Ireland, and throughout the US:
http://glutenfreemom.com/travel_gluten_free/