I've used them a good few times and mostly the charges that appear on my credit card statement is in Euros and states that the charges are "Fixed EMU Rates". I guess that that means that one Irish pound is 1.27 euros.
As to customs, up to a month and a half ago, I've never had any problems with any stuff from anywhere, for the past couple of years, but, one package was stopped. They sent a note saying that they had picked one of my packages "at random" and were "submitting it for inspection". Bye, bye, order! However, I've had several more packages come through since then, so I guess it was a one off. At least, I hope so. September 11th probably has a lot to do with this, but who knows!
Ero have changed their packaging and posting recently, so you should be safer. And you can ask them so send your order how you want(maybe without the cases to make the package smaller). I definitely would recommend them, and their prices are pretty good. Also, their Customer Service is first rate.
Hope this helps!

