I worried about it too but it really was no big deal. I didn't have that much of an issue with the prep in that I wasn't running to the loo over and over (I must have bowels of steel). I was concerned that it hadn't, er, entirely done what it was meant to, but when I said that to the nurse she kind of shrugged and I guess we just hoped for the best.
The procedure was fine. I had light sedation which makes you feel pretty even about things. It is subtle, I didn't feel out of it at any stage but later you realise time doesn't pass in quite the same way under sedation and it can make you a little emotionally disconnected (which is great under the circumstances).
No one told me this beforehand but they gave me a pair of paper shorts (!) which have a little hole at the back for The Procedure. It made me feel oddly secure that my whole bum wasn't just out there in the breeze, and I was wearing wool knee socks, so I felt almost decent despite what was going on.
My top tip
is to take a double dose of probiotics when you get home and eat something light (soup, a poached egg, porridge or similar). I was a bit gurgly and windy until I had the probiotics, and from then on everything was back to normal.
I wouldn't jump for joy if I had to have another but I wouldn't be worried about it either.