They are quite similar the difference is that Maths is more rigorous whereas Use of Maths is more applied with the focus on applying the mathematics learnt in A level to real world situations
The modules you will take will depend on your college, a typical Use of Maths structure is as follows:
Year 1: Algebra, Data Analysis(similar to S1), Decision(Similar to D1)
Year 2: Calculus, Mathematical Comprehension(Algebra + Calculus at a higher standard), Mathematical Applications(Coursework, 2 of Decision, Algebra or Calculus)
some colleges will also choose a module called 'Dynamics' which is similar to Mechanics(M1) in A level Maths
So overall they are pretty similar, however, Use of maths is fairly new and some universities do not regard it as a substitute for standard A levels Mathematics, personally neither do I, but it is still a really good qualification if you want to further your mathematical capabilities or you are doing a partially numerate degree subject like: Management Science, Psychology, Biology, Geography, Accounting/Finance, IT and (some) Computing/CS courses
Hope this helps