Unkle Lance and Aunt John to point me in the right direction.
Eden Lake is special. It's a handsome picture with handsome/beautiful leads and (generally speaking) breaks no new ground in terms of what it's about:a couple go away for a romantic weekend and run afoul of some local hooligans. What it does that other movies (and there are a lot of them with a similar premise) don't is take things farther and much deeper down. This is a movie that made me intensely angry and left a noticeable impression when it was over. I was genuinely upset at the way things turned out.
If you watch a lot of horror movies, you find that you anticipate what tricks a director or screenwriter is going to pull in a movie like this. It speaks volumes to the effectiveness of this movie that even though several tropes rear their well-worn heads, it still works. There's a palpable feeling of doom that kicks in when things start happening and lasts until the final frame, if not later.
At its core, this movie is the expression of the nightmare of the upper middle class person:torment and destruction at the hands of uncouth lower class chavs/slobs/punks/cretins. The couple has issues dealing with lower class folks and the way they choose to raise their children even before the real trouble begins. It's interesting to see how many things the couple does that are thoughtless or inconsiderate while on their trip. Of course, the young pukes are clearly the evildoers here, but you do end up wondering if there's anything the vacationers could have done that might have kept things from getting as awful as they do. Maybe not.
This movie is very adept at offering false hope. It's practically evil in that regard. It's a fascinating example of the fact that just because a movie has high production values and appears to be something very similar to something you've seen many times before, it can end up being something quite different. This is one hell of a downer.