Had mine. I guess a number of STWers are of an age that they might be needing the procedure so:
The staff involved were excellent and allow you to maintain as much dignity as possible (which isn’t much!).
I had sedative, not gas – makes you a little woozy but not zonked out.
The procedure was a little discomforting but not bad at all – no problem with comedy gas inflation, etc.
Recovery was quick and out and about by mid morning.
By FAR the worst aspect was drinking the Klean-prep – it is vile. The “effects” are as expected but not that bad.
My tips are: start the prep in plenty of time and to mix the foul liquid with orange squash and wash each mouthful down with more dilute squash. It really is the worse part of the process.