if all of your accounts already have separate e-mail addresses (like mine do) all you need to do is goto
http://www.ultima-registration.com which redirects you to
https://accounts.eamythic.com/ and where it says "Have a Mythic Master Account" put in your UO account followed by _uo and the password
then it says you already have an e-mail associated with this account, so it asks for your password again, you input your UO password and voila, you are done and you login as you did before but with your e-mail instead of the UO account name
what I'm not sure about is if you can instead at this point create a new EA master account with a different e-mail address (I think you can), IF that is the case you should be able to create a separate EA master account for each UO account quite easily without access to the old e-mail on the account.
you only need access to the e-mail if you started off by clicking the "forgot password" link