Currently being offered a price of $644 to upgrade from WTP to CW from BOS-LHR. My flight's in early May. I can't decide whether to take it or not, though. I am 6'-5" which is primarily why I decided to pay for WTP, in addition to this being a red-eye flight (BA214). Right now I think I'll wait it out to see if BA offers me a better deal the closer I get to my flight.