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.