I went back on web-chat and didn't have to wait too long to get to talk to somebody. I explained the situation and gave my email address. As I'm using a hotmail address, I was told the following:
"Ok, I see the issue here then. You will have to go through the first step of creating your account again - because you weren't verified within 24 hours, the details put in so far have been deleted. You didn't get the verification email because there's just an extra step that Hotmail users have to carry out - Hotmail accounts need to change the security settings in the email account to receive emails from us. Here is the 'how to guide'
https://www.rtb.ie/images/uploads/general/Hotmail_Safe_Sender.pdf Then go to the log in page and resend the verification link-Here is the link for that Once this is done you should receive the verification email- be sure to check your junk/spam mail after this."
I went and followed the steps and added rtb.ie to the "safe senders" list and submitted my email address again. The agent confirmed that he could see my submission and said "It may just take a little while to send - if you check back in later in the day you should get it & be able to continue!"
The issue with this is that the link is only active for 2 hours, so if I miss the email (which is possible, as I'm working), it could have expired by the time I see the mail. I asked the agent if it was possible for the link to be active for longer than 2 hours; I suggested 24 hours, but he said no.
So, if the mail does come, and I don't click on it within the 2-hour window, I need to start the process all over again. I asked how long it takes for the email to be sent, and the response I got was "It can take up to 24 hours for it to send - if it's still not sent after that please contact us again".