Issues with Subsidiary Email Account and O2 ID

Hello. 

I'm having trouble accessing my email address in a situation similarly but not entirely like what happened in the post by UsingBlueyonder.

I have a subsidiary email address. It's linked to my father's Virgin Media account. My subsidiary email address was made years ago, back when they ended with ntlworld. I've had on-and-off issues with accessing it for years, but each time, they get temporarily resolved. 

I had one of these issues back around April. It was solved through a series of phone calls resulting in my subsidiary ntlworld email address becoming accessible through logging into Virgin Media with a Gmail account and the associated Gmail password. 

In June, Virgin Media sent me an email saying that they were going to change how I log in. They said to use my Virgin Media email address and my current password.

I've now been forcibly logged out of Virgin Media and requested to make an O2 ID.  I tried my ntlworld address and my Gmail password and it didn't work. I tried my Gmail address and Gmail password and it sent me to make an O2 ID. During this, it requested the account information - account number, location, and surname - of our Virgin Media account. 

I filled this in, and it has located an email associated with this Virgin Media account that is not the one I was trying to log in with - namely, my father's email address, which is the primary address I mentioned previously. 

At this point, hopefully like in the post linked above, it has asked me something about a transfer. 

Please, could somebody explain to me as if I am incredibly poor at understanding things, how to proceed? 

Does it seem as if I am following these instructions correctly? Or am I about to make a random O2 ID and link it to our Virgin Media account, leaving my subsidiary email address in a state of continued inaccessibility?

Do I proceed with this ominous "transfer"? Will this somehow combine mine and my father's email addresses into one franken address that ruins both of our lives simultaneously? Is this "transfer" what the OP of the post I linked did, which seemed to work, or did they do something else which I have been unable to isolate in the instructions given to them? 

I am sorry for the novel length question. I am beside myself with misery and am due for an important email within 24 hours. 

Thanks in advance for any help.