Coffeecupmum - I did! I adopted DD1 when she was 10, and started the process again when she was 16. She was 18 when DD2 was placed, and had actually moved out a few weeks before intros started to live with her now husband. Having to redo the homestudy actually was good, because so much had changed since the first one - I was far more realistic, had a vastly different support network, you have to go through so much about being a parent, DD1 got interviewed etc etc.
It didn't actually take that long after approval for DD2 and I to find each other, which I was surprised at, because I was being quite specific in what issues I could handle, and the type of child placed. It really needed to work with DD1 (I was only approved for a girl, as DD1 wasn't really handling the idea of a brother at that time, although thankfully she did come to a place where I could accept DS later on), and so I was scanning the Form E's very carefully, this time actually knowing how to read between the lines! That said, I had quite a high age range (4-11) and there were lots of girls in that age bracket waiting. However, usually I think people find it takes longer second time around, because now you have a child, and you have to take so much more into account when matching
I found I had a lot of worries and fears going into it, but I think it's very normal! Would she and DD1 get on, what about money, attachment, what if, what if, what if!? But I don't regret it for a second, although DD2 is very challenging a lot of the time! She has always had a wonderful relationship with DD1, they truly are sisters, despite the 10 year age gap (there's 19 years between DD1 and DS and they get on great as well :) )
I was asked about DS, who is DD2's bio sibling. I didn't have to go through a full homestudy again, but because of DD2's issues, it took a little longer than it should have to get him home. DD2 adjusted quite well. I'll not lie, it was hard on her to go from being effectively an only child to having a noisy hyperactive toddler around, but she has always been very gentle and loving to her brother. She did regress quite a bit, and try and control me more, to try and get me to ignore DS and spend more time with her, but she never took it out on him. I would expect issues when your new child moves in
My biggest advice would be to not expect to form the same bond with child number two (or three) as you did with your first, and don't expect the same time scale to it either! It's ok if you bonded with your first on sight, but you feel much more indifferent about number two. They will have totally different personalities after all :)