I am no orchid expert, at least for the time being, but even with eyes closed I can tell whether I am holding a Phalaenopsis fasciata or a P. reichenbachiana. The shape of the midlobe is very different between these two species, and of course it is emarginate in the former. Herman Sweet's observations on the lateral lobes of these two I found to be fluid and variable, but there are indeed some consistent traits regarding the retrorse papillae on these two species; one has to take a close look to see the differences between the two species involved. Nevertheless the midlobe traits are enough, at least for me, to draw a conclusive identification. And I say, Derek's plant is P. reichenbachiana.
BTW Derek, both P. fasciata and P. reichenbachiana have trichomes on the midlobe. Perhaps you were referring to those marginal teeth, which are not found in P. fasciata.