Sorry for answering my own question here, but as no-one came back on this, i can give an up-date.
You cannot use the AIB on-line facility to set up UB as a Bill-pay option yourself, even with their new enhancements for money transfer, code-cards, etc.
However, when i rang their Phone banking service at 1890-24-24-24, the customer service agent was able to set up my new UB Zinc MasterCard as one of my Bills for on-line payment.
She initially said i should be able to do this myself, but checked with someone else, and then said she would have to set it up. Apparently the Transfer money option only applies to Personal Accounts, and not to Credit Card Accounts.
So, after a few false starts, I can now pay my new Zinc Card on-line.
As i am just using this to avail of their 9 months 0% balance transfer from MBNA, not a bad result.