Just bumping this back up.
All the letters (In capitals), are from these Across clues:-
1a. Church office (8) - benef I ce
12a, Roll of parchment (6) - scrol L
14a. Catastrophic conflict (10) - armag E ddon
18a. Wailing spirit (7) - bansh E e
All these answers fit with the corresponding Down clues so it's difficult to see where I've gone wrong.