I like SSEES. The administration is terrible, but the faculty are great (and that's what counts after all). Yes, it does have its own atmosphere with its own library, sports clubs etc. But, it's also very much part of UCL. It's next door to other UCL buildings and is only around the corner (literally) from the main 'campus' and union etc, it's nearer the union than many parts of the main campus – 60-90 second walk to the cafe/bars etc. So, really you get the best of UCL and a bit extra.
You should definitely be interested in eastern European history though, as that is understandably the focus. But, if you study the straight history degree at SSEES you have quite a lot of flexibility in taking units at other departments at UCL (e.g. the 'other' History department). Some people will occasionally (snobbishly) look down on SSEES history compared with UCL history, but I think that is mainly because of the slightly lower entry requirements; but remember, entry requirements are as much set by demand as anything else. It's kind of how some people look down on UCL compared to Oxbridge. It doesn't make UCL a bad university!