Water regs was an open book, multiple choice exam for me, it will help getting yourself familiar with the regs book, get used to the different chapters so it's easier to find the answer when answering the questions, thats the best advice i can offer for water regs as there's so much info in there you won't learn it off by heart. There are some key dates and facts that you will probably be expected to know but all will be explained on the course.
Where I did my unvented course I was provided with the book with all the info, even though it was supposed to be sent out to me I didn't get it until I turned up for the course (I didn't know the book was included so didn't know to ask). I don't have the book to hand to let you know which one. 1 day course pretty straight forward if you pay attention. Some questions may trip you up but all the info will be taught on the course. Also you will probably have to do a short practical test, mine was two separate systems and we had to list the faults. Try and get a couple of cylinder MI's and have a look at the installation requirements so you can become familiar with the different terms and fittings etc.