Stage 1 experience
ATC paper - After reading through this thread, I has an assumption that this paper was going to be easy and it was but only because I knew all the information back to front. If you have no aeronautical background then because of the range and varying difficulties of the questions, I recommend reading the PDF over and over again until you're confident that you can answer every question that could possibly come up. A number or fact that you didn't learn because you assumed it wouldn't be in the test could be the difference between a pass and a fail. There were more speed/distance/time questions than I thought there would be in this paper but you should be able to answer these if you have any chance at the more difficult questions in the numerical paper.
Numerical paper - All the questions are speed/distance/time with some variations on the theme (fuel consumption etc.). You don't need any ATC knowledge to do this, you just need to be quick with numbers and quick with digesting information. I just finished but I don't think most people do.
Cubes - There are three different nets with some questions (like the type given for practice) on each. I prepared for this by cutting out every possible net and then making questions for each. I'm not a natural cubist and I'm sure this helped me. I answered 31/40 questions but there were quite a few 50-50 questions and if I've failed, this is where it happened.
Diagramming - I didn't prepare much for this because I'm pretty good at it so I focused on the cubes. I'm sure you can make your own questions if you feel you're going to struggle with it. Try to answer the first few questions as quickly as you can so you have more time for the more difficult questions at the end. I'm confident that I passed this.
Ask on here/PM if you have questions.