For a kick off- knowing before you start university that you a) plan to go 'abroad' (in its vaguest sense and b) you want to, or are indeed cut out for 50-100,000 words of research, is nonsense. People have wanted to do PhDs in their final year of university then decided it isn't for them, what makes you think before you have any inclination of university life, before you've spent weeks in archives or labs, that you want to plan that far ahead? Go for the university you think you will enjoy more- since you're going to need to be pretty strong to have a chance when you come out- even a low 2:1 has your plans scuppered, so the marks are miles more important than the university name, especially when we're talking about two well known and respected universities.
It doesn't follow league tables either- large, old Russell Group universities with big research presences are well known abroad, whether they're 4th or 40th. People will have heard of Liverpool or Manchester- Loughborough is considerably less likely, especially if they have a small department. To give an example of my experiences- Glasgow has one of the largest groupings of historians in the UK, and among the large (35+) staffed departments, it came top in RAE for average score and percentage of world class staff outside of Oxbridge and two UoL Colleges. In addition, it houses the Wellcome Centre for the History of Medicine (Scotland), the Scottish Centre for War Studies, the Andrew Hook Centre for American Studies, and the Centre for Business History in Scotland, coupled with the largest grouping of Economic and Social Historians outside of the LSE. To this end, it wouldn't matter if Glasgow was 5th, 15th or 50th in some journalist's league table, this area of the University is well known abroad, and has numerous American, Canadian and European Academics. Several recent graduates have went on to other specialist centres abroad for PhD work, including private American Universities and German Institutions, and likewise they take on graduates from similar places. The fact that its the best part of 600 years old and is part of a large city also helps.
In sum, wondering if the man on the street in Baltimore has heard of Durham, doesn't really matter. The academics in Johns Hopkins University (y'know, the people you need to impress) will have. To this end, there will inevitably be centres at Durham where specialist activity takes place (Universities have to pool skills and develop centres like these, thats how research happens), and if you so happen to be an undergrad in a department attached to it, it certainly will help. If you show then a third class degree though, you can forget it, so I'd start worrying about that, before you get ahead of yourself.