I had 2 hour (or in 2nd year one was 1 1/2 hour) exams for 15 credit modules and 3 hours for 30 credits, with 15 minutes reading time.
Most of my first year papers required at least one essay and one problem, with the rest of the questions free choice.
In a hall where you couldn't take anything with you except writing tools, and student ID (really frustrating after first year where you commute and have to find somewhere to leave your stuff!) and there was a seating plan outside like for A-levels.
Past papers for the last 3 years at least were available online, for some exams it was very easy to guess the essay questions that would come up, and we generally discussed at least on past paper, or some of the questions from it, in a revision lecture a few weeks before the exam.
Essentially, mine were very easy to prepare for and easy enough to understand the process.