not much help now I know, but I know when I bought japanese rail pass, the cheapest place was from this tiny little office in a building on dawson street dublin kind of opposite trailfinders, sorry I can't be anymore specific, will try and remember name of place it i can or how I even found that place, it wasn;t like a travel agency but sold the tickets and had lots of other stuff on japan
rail pass definitely a lot cheaper if you are going to do a lot of travelling and train system over there is great for getting around,