I’m in the early stages of travel to London end of February for about 10 days.
I normally use British Airways from Phoenix to Heathrow. As I was playing around on the British Airways website, I found that flying nonstop from Phoenix to Heathrow is more expensive than flying open jaw LAX to Heathrow to Phoenix by about $200. That included the price of a flight on Southwest to LAX.
I probably won’t book my flight until October unless I can find a better fare.