Fire drill has left me in a lot of pain.

Evilm

Then tell them that when they do the drill they need to either have a firefighter standing by or phone one just as they start the drill.

They want to make that your exit strategy then they are the ones responsible for ensure it is treated like a real fire. If they don't want to do that then they need to fix the issue of that being your exit strategy.

Honestly.. I'd consider telling the H&S to tell you what day it will be and that you will take a paid holiday day to avoid the situation entirely (or will work from home that day)!