Apologies for stealing Brendan's thunder, but Tramp's extremely challenging puzzle has exhausted me for the evening. Thanks to Tramp!
I managed to complete the grid with one question mark (3), but it was an extreme challenge.
FOI 10, LOI 6,8. COD 19, with 16, 2, 21 and 24 worthy of consideration.
Some clues required rather specific general or technical knowledge, will say no more to avoid spoilers. The effort was enjoyable, but I hope other forum participants will find this Prize more tractable than I did. :)