If you want to become a lawyer, the two usual routes are
A) Do a law degree. Then take the LPC or BPTC.
B) Do any other degree than law. Then take the GDL, and then the LPC or BPTC.
To get on a law degree, your A-Levels can be pretty much anything. All humanities, all social science, all STEM, mix of all. For any other degree than law, the course-specific requirements will vary.
But outside of degree entry requirements, LPC/BPTC/GDL have no A-Level subject requirements. Law firms do not either; some have an ABB+ threshold but this is not attached to subject combinations.