If the UK isn’t at war with Japan and doesn’t plan to be, then all its moves will be non-combat moves.
If they are at war with Japan, are making combat moves, and it’s a friendly game, it probably doesn’t make a difference.
But no sneaking past Japanese ships to take Dutch territories at the beginning of the combat move phase, then provoking war with Japan later in the turn. It’s also my understanding that you can’t non-combat units past Japanese ships and then non-combat units into China, provoking war.