The bowel prep I had was taken before going to bed as well as the morning of the day before. so I was thinking more along the lines of waking up with that urgency and subsequent hours of toilet torture that follow.

True enough you could skip sachet B though and save yourself the afternoon.

I don't know what other preps are on offer (or even what the one I had is called) I've been fortunate enough to only have to have the one colonoscopy, so I can only draw from that one experience; I'm definitely not a prep expert or anything like that.

Edit: now that I think about it more, I think I might be misremembering; and the subsequent sachet is taken the morning of the colonoscopy rather than the day before... It was a while back, and I was going through a cancer scare at the time, so the specifics of the prep are fuzzy. But I do think you're right, Im probably thinking of the day of the colonoscopy, rather than the day before. You would be able to skip the procedure (which honestly isn't a big deal anyway, providing anaesthetic is used ofc), but not the prep you've already induced the night before (which is a big deal, and will likely ruin both your underwear, and your morning).

You will encounter every day people asking you, why you are not on the plane.