Here I am SimonGthanks for wondering, and the answer is - not very well, so I'm relieved to hear I'm not the only one. The only ones I've got are 24d -d - rag-ons (for that -because of dons, I tried to make 20d uni, but can't see it) 14ac idi -idiot without "to", 19d ria - drowned valley, and 29 ac - rue. Not much help
As for the theme - first of all I wondered if it could be insects - dragons, and an anagram of 30ac could be Diptera. Is it worth considering that they're all 7 or three letters?