Great that you've managed to do it!Thanks Alaria. Yes, I went through this page in a hurry yesterday and it is the below point which had me a little confused
"Attention! A sponsor and a Primary Applicant have different UCI numbers. If you have received AOR1, it has sponsor's UCI. Do not use it! For more details about UCI number please see "Questions and Answers" section below in this post"
But I have managed to link this morning. Thanks!
I realize you don't need this answer anymore, so will leave it here for the "next generation" who haven't linked an application yet.
You don't need to wait for AOR2 and don't need PA's UCI. If you have it from a previous visa application, great, you can use it. If don't, then you can use passport info and place of birth to link an application.