A BA engineering source known to me (being vague deliberately) today has reported that the current gossip is that a valve in the fuel pump is currently a major suspect. It would appear that the fuel flow around it causes turbulence and that they (CAA/RR/FAA) have been able to reproduce icing and fuel flow restrictions under test.
The fuel pumps in the 777 are not engine specific and the architecture differs from that on other aircraft, so whilst the authorities may never be able to say with certainty what caused the crash, the current thinking is the probability is fuel and fuel pump related.
If so, then there could be some redesign of the fuel pump valves in the near future.