If you're in Dublin, then Grape'n'Grain is probably the handiest; but they only deliver to Dublin. I've been getting it from the Homebrew centre in Clare. It's not listed on their website, but if you e-mail Brian he will order some in for you. It may take a couple of weeks, but €8 for 3Kgs is pretty good. Bob in Glengarriff does grain too, but I've never bought from him. After that people use the UK shops for speciality grains.