Right ok, you've undone them both.
It could be that a previous owner has over tightened the pinch bolt (the one that goes sideways) and its distorted the distributor. In that case, remove the bolt completely and with a suitable screwdriver, try to open out the slot on the locking plate.
To repair, you will need to do a bit of careful filework to the damaged area and this will mean the distributor will need to come out.
If it's not that, then the distributor has become stuck in the block. Not unheard of but patience and plenty of penetrating oil will usually win the day. If the engine is running, try to get the block up to running temp as it may break the join.
Arwyn
