<p>Given that's a bit of a minimum I think you should concentrate on the "First Class" standard, which is typical for most of the courses at Oxbridge...</p>
<p>...I've seen on the program pages for various courses at Oxbridge that "First Class" has been taken to mean as low as 3.7, (for example here at Cambridge, First means 3.7 <a href="http://www.jbs.cam.ac.uk/programmes/mphil_management/entry.html%5B/url%5D">http://www.jbs.cam.ac.uk/programmes/mphil_management/entry.html</a>) ....and and as high as 3.85 (again at Cambridge, but a different subject <a href="http://www.admin.cam.ac.uk/univ/gsprospectus/subjects/international/international1d.html%5B/url%5D">http://www.admin.cam.ac.uk/univ/gsprospectus/subjects/international/international1d.html</a>)</p>
<p>Depends on the subject and intepretation. I do know that GPAs vary massively from subject to subject - at Stanford the average GPA in the polisci department is aparrently almost 4.0, which may explain the above variation, since the second example is from the IR department.</p>