Just used Orbitz last week to book SEA-LGW-WDH. I found the fare on ITA. I couldn't get the entire itinerary on Delta's website because the second half of the itinerary is on a non-partner airline. ( Sadly, this means I'll miss all those miles, but it was a very large price difference). It also meant a paper ticket (ugh!), extra charges from Orbitz, no bonus miles from Delta and inability to see/change the seat assignments on the Delta leg, but both price and flight connections made it the best choice for me.