This lists Postgraduate and some Undergraduate O.R. Courses in UK Universities (in alphabetical order). Courses that are stated to be "part-time" do not offer a full-time mode of study, but courses that are stated to be "full-time" will usually accept part-time students.
Also take a look at the NATCOR website. NATCOR is a collaboration between six universities to develop and deliver taught courses in Operational Research to PhD students. It is part of a drive to deepen and broaden PhD studies in the UK across the mathematical sciences.
There are many other undergraduate programmes that include elements of O.R.. Details can be found on the UCAS website. The amount of O.R. in such courses varies widely. Applicants need to contact the relevant universities to determine the O.R. content of courses.
NB: In publishing this list of postgraduate courses, the Society does not wish to imply any approval of their content.