I got something similar, went to the end of the process and when I pressed Exit it said error of some sor. I rang them as I tried it twice and both looked perfect until the very end, anyway they said the purchases are actually on the system and they will get around to processing them basically. I did those last Friday and the money has still not come out of my account and no confirmation email either, I expected it to be quicker like most online purchases.
I will wait and see if it actually does work as intended, I have no other option for buying them, I actually got the debit card specially for this reason, they don't accept bank transfers and even if I wanted to pay €10 (I think that is cost now) for a draft my bank won't issue one payable to An Post!