This page on the website of the Oriental Institute at Oxford University lists the different possibilities of studying Yiddish:
"At Oxford, Yiddish can be studied both at the undergraduate and postgraduate levels. Undergraduates reading Hebrew or Jewish Studies (in the Honour School of Oriental Studies) have the option of taking a paper in Yiddish literature. Undergraduates reading for a degree in Modern Languages can offer Yiddish literature or Yiddish linguistics as a Special Subject.
At the postgraduate level, Yiddish forms part of the programme of study for the M.St. in Jewish Studies and of the M.St. in Modern Jewish Studies (both under the auspices of the Faculty of Oriental Studies).
It is also possible to read for an M.St. in Yiddish Studies (under the auspices of the Faculty of Modern Languages)."
See also the individual entries for these three places at Oxford University where Yiddish is embedded.