Thankyou everyone for the advice and links, I've just found the Search function, so will employ that more in future
Just tried a single mission at 88% (just the camera turned on), and managed to complete the mission and sink a destroyer that was being a bit of a nuisance. Huzzah! My first manual kill, I must paint a little Rising Sun flag on my computer to celebrate!
And now I'll stop cheering, because sinking things with manual targeting seems to be common currency here
