Paul, I know that your apnoea has a specific cause, but I did a bit of light googling and it turns out that there are some foods that will trigger it.
And I know that this will be hard to hear, but in the hours before bed, stay away from:
Fatty meats (especially pork)
All dairy products, (except maybe a splash of milf in your tea) <-- I made a typo and it's staying.
Processed carbs (which is a bloody minefield, but you can help yourself by looking at the sugar content)
Chocoloate
And this last one is weird, but... bananas. They trigger mucous production which make snoring worse and will undo what the CPAP is aiming for.
I'll add the usual disclaimer that I am not a doctor and not qualified to give medical advice, though everything I have said above is perfectly safe unless you're a monkey.
I hope the treatment starts working for you soon and you get your license back mate.