Fingers crossed for you Herbie! And, importantly - PLEASE don't worry..just remind yourself that it is much, much better to be checked out, and IF there's a problem it can be dealt with promptly, rather than not be checked and not know!
I've had a couple of colonoscopies in the last four years, and both were negative (hooray!). However, unlike Piers' unfortunate experience, I didn't have any sedative or painkillers prescribed, and really didn't need them - so it's not a definite that there's pain involved.
(And, clearly I was born a geek, but I found it fascinating to watch the process on the operating theatre's TV screens and chat through the event with the lass controlling the camera. (I've seen 'poo' in a new light! 💩😂)