Yesterday I expected that the vaulting had all fallen down since nothing showed above the level of the parapet. But as your attached diagram shows, the parapet level was right at he top of the vaulting, not the bottom of the vaulting. The wooden roof almost all burned up, and the lead roof tiles it supported all fell. I have seen pictures taken within that show some of the ceiling vaults standing and some fallen, no doubt because of falling roof timbers and lead tiles. I don't know what percentage of the vaults still stand.I think it was mentioned already, but at least the building had stone vaulting... so it was only the beams of the roof (and spire ) burning... hopefully the stonework will be unaffected.
Here's a picture for anyone - who like me - likes pictures... it helps visualize what was flammable and what will hopefully still be standing, as long as the temperature of the blaze didn't affect the stone.
I hope the roof will be rebuilt with more fireproof materials.