Thanks again! Sorted 16a/17d. Failed to find a suitable synonym for boast though but 'in opposition to' and 'female adviser' with the letters I have suggests there must be one that fits. Tried my usual online thesauruses and found that my Rogets had been culled and probably went to Oxfam. Haarrrrumph. (Could be I've got the wrong answer of course).
Oh, and Chambers doesn't appear to have the abbrev for corps in 16a. A few too many things like that this week for my linear brain. Couldn't have solved 17d without getting that one, never seen the waterfall word before and that didn't show up in any online synonym generator.