VK moved to the North to fill the void left in Zone B by the loss of the daily EY service as far as I am aware.
Not sure the exact reason behind CO's move, it will make travelling CO more pleasurable than using the South and I think BAA have/are increasing their security space in the South which has encroached on where CO check in now and BA need to save money and each desk I think (?) costs around £100,000 per year to operate so BA are losing Zone F and concentrating on just Zones C, D and half of E, especially with the introduction of the new baggage facility (TBF) at the North allowing BA to check in bags to any destiation at any desk.
I head CO were having Zone F desks 7-20 I think, the current 'Bag Drop' desks for BA, if true who will be taking F1-6?
Also does CO really need so many desks?