I’m a bit confused with the preamble. What does it mean by (U), and does the shape created mean something. I assume the SE riddle should end in S. Having never seen or read the NW riddle I had to google it. 16 cells I think, with 39/40 in total.
All in all, this was a very enjoyable puzzle, so thanks to Xanthippe. About 90 minutes to fill the grid, followed by about 4 hours of torture.