The utilities companies have been at this for years, pretending they're giving consumers 14 or 28 day's credit when in actual fact it will only be 2 or 3. Note the small print somewhere on the invoice where it states that it may take anything from 2 to 5 days to have your payment, electronic or not, posted to your account. This has nothing to do with banks or financial institutions, it's their own internal admin time.
A number of large Irish companies use service companies like Fuji to print and distribute their invoices, statements and other customer documentation. They do this in places like the Netherlands because they can get better bulk-mailing prices from there than the Irish companies can from An Post. So all the printing, paper-handing and posting happens elsewhere and the documents must travel back to Ireland, all eating into the time between the date printed on the document and the due-date for payment.