I'm not sure if the cost varies from one airline to another (don't think it does) but LAX to LHR nonstop through AA or BA is $105 in, $215 returning through BA or VS on a ZED. Of course, it's all distance-based, so you should look at making your way to JFK or another major airport out east (LAX-IAH-JFK on CO, perhaps) on your own airline, where it's free, then ZED from there to LHR. Looks like $90 into LHR on AA, $200 returning. Hmm, guess that's not much of a savings, but even then... keep your eyes peeled, and see if you can't just get on a flight from IAH or EWR on CO.

To book a ZED, there should be some link from CO's employee website. NW takes us to http://ifc.id90.com, but it doesn't have Continental on there.

If you go through NW, feel free to send me a message, I'll do what I can to look up our LHR offerings through MSP and DTW. By then, I might be back on NW and might be able to look up DL (I'm no longer an active employee, and haven't been able to check their site yet, even though I have an account).