Hi mathsman, if you reread the preamble you will see each of the 9 unclueds requires an insertion in an unchecked cell, here i to ix in the more common 1 - 9 to make 9 expressions.
Enjoyed this despite having to alter a couple of the unclued ones once I got 1 down - quite clever - some of them had more than one possible answer until I got them all (if that makes sense).