Taken the plunge today - booked the 787 going out and 777 coming back. Gives me a few hours leeway if there's any issues with my KLM positioning flight to AMS.
Couldn't do the 787 on the return leg as wouldn't get back to AMS in time for my connection back to MME.
Not going to ditch the last leg either and jump on a one-way to NCL from LHR...will only save an hour or so in the end.
Thanks for all the advice and now I just need to decide where we shall stay in Tokyo!
UTFB.