Thanks everyone for your comments and advice, we're currently booked on the 25 and you've offered fairly compelling reasons not to reconsider.

Re the return, following a couple of weeks of meandering around the South Pacific we're heading back to LHR via PVG so don't get a choice of times. Interestingly that leg will be a first F in a 777, and first NF, having always drawn OF on other routes where NF and OF co-existed. Frankly, F is F but can't see how the privacy of the front end of the 744 can be bettered.