Try Council Travel, at http://www.counciltravel.com
. They offer student airfares for cheap on major airlines like Continental, and all you have to do is pay $20 for an ISIC (Int'l Student Identity Card), available from your local Council Travel office. Since you're in LA, getting one of these shouldn't be a problem, as I'm sure they must have an office out there, if not several. They're usually near the universities, such as Georgetown here in DC.
The fares they're offering right now are $463 R/T on Continental, $480 on USAirways, $499 on British, $505 on Delta, and $511 on Virgin, among others.
If you're planning on travelling two or more times a year, I'd recommend that you join up with Bestfares.com travel club. It costs about $60 to join, but the savings pay that off in the long run. Currently, they are offering a roundtrip from LA or Orange County to London (no airline specified) for $358 R/T. Check this deal and others out here: http://www.bestfares.com/travel_center/desks/story.asp?id=10089904
Otherwise, you can always take a gamble on Priceline.com, which allows you to enter a bid on airline tickets using a credit card (if you have one). The thing is, Priceline does not allow you to select your itinerary or your departure times, while Bestfares and other travel clubs do. However, you can save a lot of money using priceline, and if you have a Student Advantage card, you can save $25 off a winning bid. Find them at http://www.priceline.com
Hope that helps!