Cebu Pacific A330s are in a special high density configuration of 9 across instead of the normal 8 across. They have 436 seats, certification limit is 440, which is more than some A380 operators have. The aircraft are intended for Philippinos working in the Middle East who are smaller than the average westerner, don't mind being crammed in together and are price sensitive.
4 hours is the MAXIMUM time you could endure this for.
Philippine Airlines often have cheap fares from Australia to London and are a full service airline. Not up there with SQ or Qatar Airways, but worth a try if the price differential is noticeable.