As someone who is doing re-takes this year, I like to frame it as if everything is going as planned. You really get to understand yourself and how you learn this year as you prepare for the examinations. You'll have a few days of exams and it'll be over. In terms of where you sit it, that's entirely up to you. I will be sitting them internally as it makes my life a little easier in terms of organisation but I may choose differently in a few months should my opinion on the matter change. If you feel uncomfortable re-taking them at your school, simply apply to a local college. Many people re-take exams so it's nothing to sweat about.