Anyone booking on line should be aware that you don't have to accept the ticket(s) first offered. On my first attempt, I was offered A9/10 so tried again and was offered A11/12. I kept going to see how close to the centre I could get - A21/22 are either side of the centre isle. It skipped a few right in the middle and then offered the tickets I booked.
I have just booked a ticket for this concert, i'm on A13.
Would have loved to have gone to Nottingham with so many members going but unfortunatly I am on holiday then, this was the most convenient for me without having time off work as Wolverhampton is just 30 minutes on the train for me.