Hi, i'm looking for a masters in international relations. I'm not sure where the best universities for this are. Is there some sort of Masters league table? I'm not too fussed where the degree is, but preferably in an English speaking country.

In the UK a masters in International Relations would not be an MBA, but an MA, MSc or MRes.
Among the best places are Manchester, Aberystwyth, Lancaster, Exeter. (Keele, Birmingham, Leeds and Sheffield also have good reputations).
It completely depends upon what aspect of IR you intend to study. Many of the best places will be particularly theoretical

I think Durham University in the UK is a very good university too

Durham is a fantastic uni, but doesn't have a great rep for IR. Saying that their Politics and Geography depts have an amazing research cluster called politics-state-space, with people like David Campbell who I adore. If you want to do more critical IR, like Rob Walker's critique of the state as a product of spatio-temporal relations of early modern discourse then yes, Durham would be amazing for a PhD, but for a Masters, you would probably be better elsewhere.

Thanks for your help Sleepyhead. How do you know this about those universities? Is there some sort of online resource or database that scores universities on certain courses?