No University requires 4 A levels. Some 'top' Unis, for some subjects (typically STEM and where you are taking FM), may make what they call alternative offers - a 3 A level offer plus a 4 A level offer ("AAA including .... OR AABB including ...." etc), and you are only required to meet one of the grade sets - but they will not prefer 4 A levels, because the majority of applicants will only be taking 3.