Can't switch seats!

Just checked on the Manage My Flights and the seating plan for my flight in a couple of days has switched to a refit - Hurrah!
Problem is that although there seats available in the bubble, it won't let me select them. This is the message I'm getting:
"We're sorry, the seat(s) you have chosen are not available. You are still shown in your original seat(s)."
Do I have to wait until OLCI is available and then try?
Assuming I manage to switch does anyone have recommendations about the best row to go for in Economy in the Bubble?
Problem is that although there seats available in the bubble, it won't let me select them. This is the message I'm getting:
"We're sorry, the seat(s) you have chosen are not available. You are still shown in your original seat(s)."
Do I have to wait until OLCI is available and then try?
Assuming I manage to switch does anyone have recommendations about the best row to go for in Economy in the Bubble?