Hi Geeker,
I think I had a similar experience to you, in that my solving speed increased dramatically once I'd twigged the theme.
FOI - 3d followed by 4d
I think the difficulty level very much depends on how quickly you spot the theme.
If you do get stuck there is a hidden and an anagram in the acrosses and a hidden and an anagram in the downs.
There are still two clues I can't fully parse, namely 18a and your COD 13a, although I'm pretty sure of my answers.
COD - I've gone for the short and sweet 15a - simply for the image it provokes:-)
Thanks to Paul for a challenging and fun crossword.
As always, please feel free to leave a comment giving us your thoughts on the puzzle and, if you get stuck, don't hesitate to ask for a hint.
Stay safe:-)