Wrightbr wrote: Removing the distributor in order to get these out and fix the sheared bolt?
Just a further thought on this ....... Did the bolt shear just below the head, or where the threaded section meets the flange ?
If it is just below the head, then once the other two bolts have been removed or sheared off, remove the rotor and the remainder of the bolts should be reasonably loose in the flange as the pressure has been taken off them by the shearing off of the heads. Try to just unscrew them by hand .... if a bit tight still, give each bolt a sharp tap with a pin hammer or similar ... this should release them sufficiently to be able to wind them out. If still tight, grip bolts with long nosed mole wrench and wind out.
It would be worth trying this before removing the center bolt holding the rotor flange.
If eventually you do have to remove the flange, perhaps we could ask Lee to let us know what position to turn the camshaft so the key way is at the top, as if the key is loose in its slot, there is a very small risk of it dropping out if pointing downwards .... it should be tight, but I have known them to be loose ..... better safe than sorry.
Have fun.
CORRECTION ..... My reference to "key way" is incorrect, the method of lining up the two parts together is, as Lee said, is with a roll pin. I was getting my info from the parts list which gave me the impression it was a key way. However, I still would bring the pin up to the top before removing the flange so as to see that it stays in position when removing the flange.
Sorry for the misleading info.

1990 GTA Atmo, 2003 Jaguar X type 2.5SE Auto, 2018 Kia Picanto GT-Line-S 1.25