A friend of mine last year did IR with research methods. He is now in work but it wasn't particularly easy to find employment, but it usually isn't easy anyway. There isn't much offered in the way of careers advice if I'm being honest but they do have a kind of jobs fair at one of the colleges (usually Josephine Butler) in the first term where you can get information on grad schemes. I went to that and got a load of free stuff and some friends of mine got some advice on careers.
There isn't that much for SGIA specifically though. You can probably ask for advice but I never did as I knew I wanted to do a PhD. The department itself feels like it favours people who study the Middle East, which is what the department is generally known for. If you are interested in Middle East politics you might get more opportunities.
I applied for 5 universities for postgrad and got accepted to 4 of them. Durham accepted me first, which helped with the choice, but the collegiate setup of the university is also very appealing. You get to be a member of a community that holds its own events and has its own sports teams and societies. These contribute most to the campus atmosphere for people in SGIA as the department isn't on the science site with most of the other departments.
As far as colleges go, if you want proximity to the department St Mary's, Trevelyan, St Aidan's and Van Mildert are good bets (assuming you live in).