I am a musician. Can I get instrumental lessons in Oxford and play in an orchestra/band?

The University of Oxford is not a conservatory so no University music tutors give instrumental lessons.  It is generally possible to find a teacher outside the University, though this is not something which SSO can arrange.  It is always possible to find an orchestra or band of some sort to play with, since there are so many, often of a high standard, though students should not expect there to be vacancies in the best ensembles unless they (the students) are of near professional standard.