Mine was given back to me as a merit. The tutor said to add another paragraph about a certain topic and hand it back in and it would be a distinction. The tutors aren't lying when they say they're there to pass us, not fail us. If you're unhappy with your grades, maybe you could ask the tutor what you could have added to make it a distinction?
It's probably very different depending on the course, but I didn't find mine particularly difficult, just time consuming. It involved reading through a lot of different books and websites on the subject matter and arranging all that information into a structured piece, rather than merely answering the questions as I noticed a couple of people in the class doing. I'm doing Access to Bioscience by the way if you were curious.