OK, so I've since been back to the mirror/werewolves' area, and defeated them without the mirror joining the combat, so I guess that was just a freaky bug.
I'm still not through the game yet, but am so tempted to just say 'the hell with it' and start using the co8 mods, I really want to kill my NPC's for taking important loot, and am sick of filling their inventories with leather gloves and boots from random brigand encounters.
So here's another (probably silly) question:
If I install patch 2 (over my existing patch 3) and the co8 patches, will my savegames still work? Will I lose my party completely? I'd hate to see them go, now that we're at LV. 9 and all...