I had a colonoscopy about 20 years ago, part of a random screening by the NHS.
Like a few others I had to self administer the enema at home. It worked before I left, but had to travel on the bus to the hospital (no car at the time) and was very anxious about a potential accident.
But it was OK. No anaesthetic, and I didn't enjoy the "exploration", very uncomfortable, not painful.
It was interesting to watch on a monitor screen.
Husband has had a few, with full anaesthetic. His grandfather died of colon cancer.