How are you going to define relevant in terms of 'pure' maths? None of it has much use to real world applications.
Pure Maths at A-Level is entirely relevant to pretty much any Engineering, Physics or more mathematically based Economics course at University. All what I would call real-world subjects!
Infact, what is defined as "Pure Mathematics" at A-Level is really the bedrock of all the applied mathematics based subjects at University. It skips a lot of very low level material that real Pure Mathematicians would find crucial; ideas about proof, assumptions and deduction, the axioms of mathematics, all the stuff that Engineers and Applied Mathematicians (like myself!) rush over to get to the equations.