I achieved an A in Maths and B in both Biology and Chemistry at A-Level and have completed my bachelors at Queen Mary, University of London and my masters at UCL. This was after achieving an A* and a 2 A`s in GCSE Maths, Biology and Chemistry respectively.
The only change I made between GCSE and A-Level is that I learned the skill of studying effectively; something which I can help you understand too.
My students have gone on to A`s in their exams; references available upon request.