Sheffield
Aeroscout, sheffield used to publish a condensed list of questions for the ADX (wonderful and pointless waste of time and effort that it is) that was gleaned from years of exposure to the testing environment. They had narrowed it down to something like 500 or so questions that if memorised would practically guarantee you to pass it.
Studying all 2,000 questions is a time consuming excercise and best avoided if at all possible.
Nevertheless, getting the ADX out of the way first is the absolute best thing to do as it frees up your time while on-site to focus on the course and you'll need every spare hour to get through it.
Sheffield is the best school out there and has been for years, you'll find some negative posts on here about them but they are from people who failed or felt they should have been given an easy ride.
Feel free to pm me with any questions, have been there done that.
All the best.