I don't see how the state could afford to buy the land and building from the church. The church doesn't have a problem, they could sell it elsewhere,at a huge profit, if the state didn't want it. It will all be prime building land.
Huge profit?
I feel a tax bill coming on!
In fact the state may not want all the buildings and given that it is only 10% which is owned by CofE it is quite possible that this could be paid by giving some buildings back to the church in their entirety.
Also, land is only prime development if planning permission is granted.