Somewhere I think I remember reading that there is a difference in the physical fuel flow to the left and right engines - something to do with the oil/fuel heat exchanger?
Is this correct or is my memeory up the spout?
No. The engine fuel/oil heat exchanger is on the engine. It is the same on all Trents.
What is confusing you is that the hydraulic oil pump case drain filter heat exchangers are in the fuel tanks. Two in one wing tank and one in the other. These cool the skydrol that runs through them, and in so doing impart heat to the fuel in the tank. This heat is nearly not measurable.