LHR-ORD
Y>W accepted an offer at $175 + APD as I don't have OW status and would have paid for MCE.
Y>J was hovering around $1400 + APD.
I unfortunately didn't receive any additional offers W>J after accepting the initial W offer (some data points said they received subsequent offers, but not I).
Flight was J7 with 13 unassigned seats T-48, so wish I had waited in case one of the cheaper J offers came.

ORD-LHR (daytime flight)
Y>W when available, offers between $300-1000, although the cabin sold out T-3 weeks or so.
Y>J when available, offers as low as $610 to $2500. Still selling 3 seats, but no longer displays an offer on my itinerary.