Looking at the photo I don't really see how they could have positioned people in any other way. They had to get the dress in full view necessitating a gap between the Queen and bride, Sarah is standing to the right of Phillip, she's not that far from him and they had to put Beatrice somewhere so other than squashing her in on the end I think that's looks fine. There are a lot of people in the photo as all those children had to be in it too.
I loved the whole wedding, the dress - she looked beautiful - and the fact that they both looked so happy. I also thought the children behaved wonderfully - their parents must have all been so proud of them.