I had one less than a week ago.
I had the prep called Pirolax, in 2 sachets. I read it was vile and hard to take, but followed instructions to have it chilled and through a straw. I found that bit easier that the copious amounts of clear fluid, but maybe because I hate soft drinks, they make me nauseous. So I drank those through straws too.
A couple of tips... Pre measure and prep your drinks. It makes it so much easier especially if drinking during the night. Find something to do while drinking... I surfed the net to take my mind of it and they went down easier. Then back to bed inbetween. Everyones different to their reaction. I read about long long stints on the loo so was surprised that the 1st sachet did nothing until I drank the next drink, which went through me in minutes like a tap, and that was how it continued, so no long sitting and sitting for me. And also, it is usual to stop drinking 3 hours before. I would say 3, as I was still going to the loo as I waited in my gown. It was clear, so ok, but not relaxing to know you're still going!
As for the procedure, it was so respectful. A nurse settled me on a bed and tucked me under a cosy blanket while the surgeon chatted as he sedated me. I little while later I asked when they were getting on with it to find an oxygen mask on my face and it apparently all done. I do remember pain just at the point that has led to the investigations, they said no. So false memory or them being kind to help I don't know.
But, it really wasn't bad!