I've had them both (seperately) in the last two weeks. The gastroscopy, which I've had before, I demanded sedation for as I find it so unpleasant. Then the colonoscopy - as people have said here the preparation is the worst bit. Two sorts of medicine, the first I had (twice) tasted not bad, but the last one wasn't nice. And the staying near the bathroom bit is vital! They said I'd sleep through it, but I dozed off, then woke up to see it all on the screen and fell asleep later. Bit uncomfortable but not too bad. If I had to have both together I really hope I would be asleep for it all.