Thankyou to everyone who's taken the time to post their thoughts and experiences. 
I'm having a colonoscopy in two days so tomorrow is my day from hell. I had a colonoscopy three years ago and all was well but things have changed and my doctor thinks I should have another one. Either that or she doesn't like me very much! 
Personally I found prep day far worse than scope day. Apart from the fact that my daughter is a nurse and when I saw one of her friends coming to collect me for my procedure, I wanted the ground to open up and swallow me. I tried to hide behind my kindle but it was no good. Then the trainee helping the doctor turned out to be a young man who goes to the same gym as me. 'I'll say hi next time I see you' he said jovially. 'Please don't' I thought. 
I can only advise, lots of cream like anusol, which has great anaesthetic properties. It saved my sanity last time. Truly my bottom was so sore I started to wonder if someone had swapped the loo roll for coarse grade sandpaper for a joke, last time. After several eye-watering 'experiences', I managed to find an old tube of anusol in the back of the bathroom cabinet, after everything else I tried had failed. It was like Nirvana - not state of relaxation, not the group! So this time, I'm well armed with a new tubeful!  Please wish me luck & I shall report back on the other side!