I had my interview for mental health nursing at the end of February and it was about the least intimidating thing ever! We didn't get literacy or numeracy tests but I don't know if that will be the same for the adult nursing students. They're not looking for someone who already knows all the ins and outs of nursing, so even if you give a 'wrong' answer to a question, it really doesn't matter a huge amount. Most of it was asking about why you think you should be a nurse, and why you've chosen this specific university, and assessing your understanding of what it means to be a nurse and what will be required of you. They ask about your strengths and weaknesses, and if you're going to talk about weaknesses you should be able to explain how you're working to overcome those weaknesses. It's a good idea to go back over your personal statement because they might refer to it in the interview. Remember, though, at the end of it they're also looking for a human being! I won brownie points in my interview for mentioning that I volunteer at the RSPCA as a cat socialiser, which went down well with the two women who interviewed me as they're both cat lovers (and I was even able to relate it back to my suitability for the course, since it means keeping odd hours when we're nursing newborn kittens and so on).
Regarding scenarios you might be asked about, a lot of it is just about common sense, and if you're already familiar with what's required of you as a nurse, it shouldn't be a problem. This sounds incredibly obvious and slightly patronising, but just relax and be yourself, and it'll come through in the interview. Don't be afraid to be enthusiastic!