Very interesting reading all these different, yet similar, feelings.
Underneath our rational, civilized world is a dark mass of primeval instincts. So we shouldn't be too surprised when the thought pops into our mind, "there's 2000 feet of thin air 6 inches below my seat and I'm going to DIE!"
If you've never experienced this, your veneer of rationality is just a bit thicker.
It takes TIME to get used to the view out of the window - your problem, Knievel, is that you're paying £300 per hour for the view. One solution might be to find a cheaper good view - micro-lighting springs to mind.
However, the scares will always come back at some point - a new situation, a new aircraft, whatever - get used to dealing with it. Fear is good, anyway, in moderation - it keeps you sharp.