I had one with gas and air a couple of years ago - I just didn’t fancy being woozy afterwards, and wanted to know that I’d take the results in properly. It was pretty uncomfortable but perfectly manageable, and they gave me a cannula so that if I changed my mind they could instantly have sedated me after all. There was a wonderful nurse rubbing my stomach and squeezing my hand and telling me how well I was doing, and to be honest the whole thing felt so like childbirth that I felt a bit cheated not to be handed a baby at the end of it - but I said that and the doctor said it would be a bit frowned upon for her to steal one for me.
I think the main problem with turning down the sedation is that you retain more of your inhibitions. They have to pump you up like a football to inflate the colon and get the camera through, and I just got more and more full of air until I felt like I was about to explode, and eventually the nurse said “you do realise you’re allowed to fart don’t you?” And the doctor said “oh my God, yes, do fart!” I hadn’t consciously been restraining myself, but obviously the instinct preventing me from farting in the consultant’s face was still intact, which presumably it wouldn’t have been under sedation!!
On the plus side the recovery was immediate - I felt absolutely fine, took in the full joy of being told everything was clear, and went home to eat steak to celebrate!
The prep is utterly grim though. I was really strict about the diet beforehand so was starving and miserable from several days of incredibly bland food (including my birthday). Then the drink was enormous and vile and despite having it super chilled and alternating with sips of fizzy lime to cut through it is still absolutely revolting. And then you’re up all night on the loo - though I didn’t get the kind of cramps you get with a stomach bug; just a very insistent emptying. I second the advice about Vaseline, you’ll get really sore otherwise.
Ugh, haven’t relived it in quite such detail for a while! It’s not fun, but all the staff were completely wonderful when I had it and it’s an incredible, life-saving technique. Good luck.