I would have thought @MarmaladeSandwich7 that if you had one several years ago, that you would be pretty au fait with what they entail?
Re: those who are due to have one and are dreading it. You don't HAVE to have one, and can request a CT scan (with contrast.)
I have a friend who had a positive FIT test (blood in poo) and immediately her GP contacted her and said she must have a colonocopy, as it's a sign of BOWEL CANCER. 'You NEED to go and have a camera shoved up your bum' were the GP's words to my friend.
Firstly, in 93% of cases, blood in the stool, is NOT bowel cancer, and also, you don't HAVE to have a colonoscopy, you can request a CT scan (with contrast) of your bowels/intestines. They don't tell you this though, because it's 3 times more expensive than the colonoscopy. My friend refused the colonoscopy (for several personal reasons,) and they let her have the CT scan.
A colonoscopy is horrible. It's intrusive and uncomfortable, and the prep is vile. Also, there are a number of risks with it. I won't name them, just google them. (Google downsides to colonoscopy.)
The only 'advantage' of it is if they find something (like lumps or polyps) they can remove them immediately. If you have the CT scan, and the scan picks something up, you will have to go back, and still have the colonoscopy anyway. In around 80% of cases though, they find nothing at all. (With the colonoscopy or scan,)
They will have you believe that a colonoscopy is the 'Gold Standard' medical care, purely because they can chop anything away if they see anything whilst the tube/camera etc is up there! They also tell you that colonoscopies will see/detect more than the scan. Not true. Scans can occasionally miss things, but colonoscopies can too. They don't tell you the downsides to colonoscopies, or the fact that some things (growths or small polyps etc,) are probably better left untouched anyway!