Hiker, that is really rough! In about a month you'll be making some friends at school, but I know this isn't helping now. Is the school available for you? I mean, are some facilities open? Is there a way to get a head start, such as going to the library and hanging out in places where people might be? I'm not in the London area or I'd invite you to drop in. There are places in London where Americans hang out, but I'm not sure where. Texas Embassy by Trafalgar Square springs to mind. (You will find it easier to slip into American groups for now...then when you are more settled, the English firends will come.)
Frankly, I'd say the first thing to do is find someone you can be with, I mean a friend, to do things with. This stage got me through many many initial hurdles. Keep an eye on the Expat meetings and events section on this forum for any London get-togethers.