Why not book a direct or connecting flight ex-LON?
Because the initial flight was purchased months ago when I was able to get an $1100 RT business class fare for SEA-LHR-BCN. I've already called BA to see if I could skip the LHR-BCN segment and treat it like an open jaw and then book another OJ LHR-CAI;CAI-BCN but they said it would be a $500 change fee plus the difference in fare. They also said that if I skip the LHR-BCN segment they would cancel the rest of the ticket. So, whatever I do, I'm starting from BCN.