I actually think ANA's 787's are some of the most uncomfortable long-haul planes I've flown. Not sure what aircraft LHR-TYO uses, though.

Things have gotten a little more bearable since they've installed the footrest. And you do get good legroom with the slimline seats. But ANA's 9-abreast 787 seats are ridiculously narrow (I'm not a big guy), and those seats don't recline much. I fly TYO-YVR/SEA on these, which are not long flights, but they sure feel very long with these seats. I actually think 10-abreast 77W's are more comfortable. I can't comment on JL much, since it's been a while since I've flown them in Y internationally. But based on what I've read, it just seems like they have superior hard product.