Finally cracked it! Thanks Sammy - you're dead on with FORMATION- it fits with AFFRAY and gives me 19 across 'Increased the quality of' as ENRICHED. The 'ICS' ending I had (MECHANICS) is infact ION as 'Water holder' is CANTEEN not CISTERN (!)
It was one of those crosswords where you can find an answer that fits, but it's wrong, and throws you off for a lot more of the puzzle.
Anyway, thanks so much for your help, Sammy. I am finished and relieved! :)