Going to be honest, before attending LSE I thought it was going to be boring and filled with just work. I was wrong. Just ignore most of what you see on TSR - most complaints are from people who aren't even studying here and anyways, it's the complainers who are often the loudest.
LSE is really really really what you make of it. Join societies, clubs, attend events, etc. and you'll realise that the world truly is your oyster. I'm only a first year just last week, I competed in sports outside London, attending huge networking events, went for a fancy ball, had fun dinners with my societies, listened to a talk from a world leader, attended a classical concert on campus and even did a practice moot! Even this week I have tons of events coming up (cough like a costume party for halloween by the sports union).
LSE is fun, period. So long as you make it fun and put in the effort.
edit: on things like you mentioned, like *****y teachers and cliquey internationals, I think you'll find them everywhere (though to be fair, the locals are often cliquey as well).