Just to clarify that 'Pure Maths' means something quite different at university to at A-Level. Whereas at A-Level, all that isn't Statistics, Mechanics and Decision is lumped under 'Pure', at university, almost all of the 'Pure' section of A-Level would be considered as Applied Maths, with a few exceptions like some proofs.
I'd advise making sure that you're definitely happy with the course content before narrowing it down to just a Pure Maths degree as it may be different to what you'd expect given the A-Level module names. (Obviously if that's what you're aiming for then you can ignore this advice).