Chances are most of the maths will be the same in the first year
And if you work hard you could probably swap courses to straight maths after first year.
Warwick is a good school for maths, go for it.
Ok I looked it up. It's a maths/computer science joint course
The year 1 maths component is Foundations, Analysis, Vector and Matrices, Probability A, Linear Algebra, which is pretty much what i did on a straight maths course. Except I also did mechanics, which I hated, and maths methods.
This course would probably be fine to swap to a maths course where you selected units predominantly in pure maths in years 2 and 3, but not one that included mechanics or mathematical physics.