If you're interested in becoming an astrophysicist, you'll need to have a strong academic background in physics and mathematics. To get into a top university, you'll need to achieve at least three A-levels with grades of A*AA, including an A* in both physics and mathematics. You may also need to have achieved an AS level in the same subjects. When you first start out as an astrophysicist, you can expect to earn less than more experienced colleagues who are leading research projects.
As a beginner, you'll likely be working closely with your supervisor as you gain experience in the field.