Unfortunately the comments and questions seem to have fallen across two discussion threads, so my apologies if this question has already been answered.
12 across my solution has thrown up 'water channel' as extraneous words, but there is no link with the extended down clues. Have I missed something?
Also I had monopolising as an extraneous word in 11 across. It seems to be used to mean including - I am not sure if that is an appropriate use of the word. This is a a shame, because otherwise it was a good puzzle.