The unclued light at 14A is evading me: oli? I have olio or olid as options but neither seems to make sense.
Also, I don't have all the spare letters to make the phrase. I have spare letters from 24A, 35A, 40A, 5D, 6D, 15D, 25D and 30D so am 3 short. Are these the right clues and which other clues should I be looking at? I don't want the letters, just the relevant clues please.
The clue numbers you list are all correct. The three you are missing are at 39A, 42A and 21D.
Once you have spotted the theme you will know which of your two words to enter at 14A.
For the spare letters I have A FILE ANKJAD so I've done something wrong. I have UTTER, ARRANT and OLIO/D as my words to go with the last bit of the phrase but I'm just not seeing it.
Of your spare letters the J and one A are wrong but you can almost make out the phrase from what you've got. Anyway it appears in the grid in a contiguous series of 11 cells starting horizontally, then diagonally and finally vertically. The three words you mention go with the first part of the phrase not the last.