Hello. I hope your colonoscopy goes well. Most people find it tolerable, but I'm afraid I found it absolutely agonising and I would never, ever undergo one again. The sedation didn't work for me. However, all I got was a quick injection before the procedure and they were totally unconcerned that it hadn't worked and I was in pain and they were quite nasty to me. They said it was my fault for being so afraid, as this stops the sedative from having any effect. I've come across other people who've also had bad experiences (my aunt said it was worse than childbirth for her).
I'm sorry to be so negative. I wasn't sure whether I should post or not, but decided that it's best to be honest about experiences on a forum like this. Hopefully your colonoscopy experience will be nothing like mine, and it's good that your consultant is doing it, as I presume it's someone you trust and they obviously must have a huge amount of experience.
For the sake of balance, too, my brother had a colonoscopy the other week and felt nothing more than occasional, moderate discomfort.