Thanks to Brendan for an extremely challenging New Year's Prize. I despaired of finishing, but set the puzzle aside for a while and cracked it upon returning. Slow going from start to finish, but struggled particularly with the SE quadrant. FOI 4, LOI 26. COD 22, the clue that held me up longest.
It's been a long week at work, so perhaps it's fatigue, but I wonder whether other forum members found this puzzle difficult. Happy New Year and have fun!