Hi kevin,
I am flying to manila in December.
I booked the Seoul ticket for £777 (actually £920 with the ncl leg added)
I m then flying with cebu pacific to Manila.
it was by far the cheapest way to do, although it does have to be within the dates of the super cheap tickets.
when i was looking at doing it all on OW, it did look like BA then Cathay as the best choice.