The Oxford mathematics course gives you massive amounts of flexibility as to what you wish to study after the first year. You'll usually study between 4 and 6 topics a term simultaneously.

In terms of tuition, my average day has 2-3 hours of lectures and I work through about 10 problem sheets a fortnight. Classes do not exist as such, what we do have is an hour long tutorial with a professor or doctor (post-grad on some occasion)s who specializes in that area once a fortnight. The tutorials are usually 2 students to one tutor, and in later years 1 to 1 as you become more specialized. These tutorials consist of going over the work you've done on these problem sheets.

EDIT: All the course notes and problem sheets can be found here: http://www.maths.ox.ac.uk/courses

I'm not sure how much you know about the university of oxford in general, but I'll mention a few important things:

The university itself consists of over 35 separate colleges, each with 150-700 students studying for degrees or doctorates (well, except for All Souls College, but they're something insane.) These colleges run semi-independently of of the university, The university sets the syllabus and exams and provides the lectures, but lodgings, tutorials and food are provided within each college.

I'm currently in my first year at the University of Oxford studying mathematics.