Took me ages to get going with this but once I had really struggled with getting the first half-dozen in things got easier. My FOI 17 followed by 19,18. COD for me was 9,1 just for Tramp’s ingenuity in getting such a name into an anagram! Defo on the harder side today!
i seem to have a different answer, then. apart from the vanished R. it works perfectly, using the "down" as part of the wordplay rather than the definition.
Jono, despite your hints I am still struggling with 5a (and hence 8d). I wonder if my crossers are wrong? I have C and I for 5a and A & D for 8d. I'd appreciate your confirmation or otherwise.