Moviprep

Hi.

I'm having a colonoscopy on Friday at 1:00pm. And the instructions for an aftenoon procudures says to take the first dose of moviprep at 7:00pm the night before and the next one at 6:00am on the morning of my procudure  

Im thinking am I going to be up all night in the toilet with the first dose,  given it says take it over two hours, so 9:00pm before it's all taken and then it has to work? 

and will I have enough time on the morning after taking the moviprep for it to finish doing its job and to get showered and to the hospital in time? 

Laxatves have always taken far longer to work on me than it says on the box and I'm worried this will  too. 

Anyones experience and thoughts on this would be useful.