I am flying out of SFO to LHR. I have been finding fares for a little over and a little under 600 dollars, during the month of May.

Does this seem like a reasonable price? Is there anywhere else I could fly to that would be cheaper than this if I took a train for part of my trip?

yes, it sounds reaonable.

No, I don't think flying anywhere else in Europe then taking a train back to London will help you out.

if this is a nonstop, grab it quick. if it involves one simple change, i'd still grab it. if it involves two or three changes or long layovers, i'd keep looking.

i fly from Seattle to Heathrow. yes that seems very reasonable to me, especially if it is a non-stop flight.

does that include taxes - If so, jump on it ASAP. Fares have been higher this year. In the past I've usually been able to get SFO/Londonn fares in the $500 $590 range inc fees in May and a bit more in June. But this year things are higher. And even if that fare doesn't include taxes and fees it really isn't outrageous this year. Be sure to play with your departure/return dates - on day either way can make a LOT of difference.

SFO tends to have slightly lower fares than LAX. Another place w/ competitive fares would be promotional fares out of Las Vegas. But by the time you got to LV you would have eaten up any savings.

That should be " . . the $500 to $590 range, inc. fees . . "