I went along with Pilot Pete some years ago to lobby my MEP who was the "raconteur" if that's the right word, when the initial legislation was passed at the European Parliament. It was quite clear that the individual concerned hadn't a clue about fatigue or the issues involved (not bad for a Labour MEP). His view was the legislation should be passed, then reviewed and changed if necessary. His first 2 ideas came to fruition and the review showed that the legislation was fatiguing.
Legislation in the UK still requires pilots not to fly if they are fatigued or if they consider that the rostered flight would make them fatigued.
Simple solution is don't to do the flight and fill in the sick form with the simple word fatigued. No manager would dare to touch you.