Hell, I'm doing engineering with just AS maths.
Don't expect to get into any fantastic university with just an AS (pretty much everywhere accepting grades will want an A2 as a minimum) but it's possible to get by.
The sorts of maths we use do stem from further maths, so it is certainly an advantage. Much of the rest is just picked up along the way. For many universities, just the A2 is required, but it would help your application to offer as much maths (and maths related subjects) as possible.