The simple answer is that if you want to guarantee that you will take a significant amount of Mathematics beyond Year 1, you must take A-level Mathematics and at least AS-level Further Mathematics. Please see "Essentials and Admissions Process" for more information.
It is noteworthy that the Further Maths Support Programme in England and Wales offers students/schools support in taking Further Maths. If you aren't studying Further Maths you need to study at least two subjects that don't include Mathematics as part of your degree. This involves students getting an A* and an exceptionally high set of UMS mark (at least 95%). They are then required to work through the Mathematics Summer Workbook that is linked from the Brush up Your Skills wiki and secure a mark in the diagnostic test (at least 70% overall and at least 15/25 marks in each specific part of the four parts). This should be seen as an alternative route, because nothing beats taking AS-/A-level Further Maths and giving yourself time, it also avoids disappointment!
Need to get in touch with us? Ask us here