Thanks - gave it a go as I had 19 posts that were not linked.
It recovered 5 threads. Not all can now be deleted, which I am not too worried about.
One says it can't find the post in the database to view the post.
The other where it merged two threads together (making a 4 post thread), I could delete the last 2 posts, but the 2nd post you can't delete as it says it is the first post in the thread (which it isn't now) and has dependant posts beneath it (which it doesn't)
Anyway I am not too worried, but just reporting back my findings.
HOWEVER! - it found the very first post I made with threads back in 2001 - meaning that my forums are at least 7 years old. Although they go back a couple of years further in a smaller incarnation. So I am happy