Some online shop recommending..

My Mexican Shop - Based in Ireland and will deliver throughout Ireland for €8 and within Dublin for €6 (though that charge covers up to a very generous 30kg), with the ability to collect your order in person if you are based in Dublin. Their selection isn't enormous but does cover things like epasote, achiote and dried chiles that are hard to find outside Mexico.

mexgrocer.co.uk - The selection at MexGrocer is larger and they deliver throughout Europe. For delivery to Ireland by courier they charge £17 for up to 20kg, they will also deliver by standard mail, the prices are listed on their site.