I had lots of colonoscopies when I suffered with UP. My problem was always proctitis. A few times my GI doctor could not go up as far as he would like because of the ulcerations and he feared perforation. This annoyed me somewhat because he KNEW I was flaring and still insisted on doing the colonoscopy. I remember he did not want to do them if I were on a high dosage of prednisone either.
The prep I was always prescribed was the Nulightly . I hated that prep, but for some reason my GI said for patients with UC it was the safest. Not sure if this is true though. I know there are a LOT of other preps out there. When hospitalized they gave me magnesium citrate. It tasted a bit like 7Up..not bad at all.
Like Peety stated, the worse is the prep. I would mention your episode of waking before the test was completed though. Maybe they will be extra cautious about the amount of anesthesia to give you so it won't happen again.
Best of luck!