I can't see a continuation of this in general Land Rover chat so I shall add my experience here. When I first got my TD5 I was driving over some pot holes and it went into limp mode and the yellow engine light came on. Over the next couple of weeks a number of attempts were made and suggestions tried, including the accelerator potentiometer, fuel pump, oil in loom etc. to name only the most usual of the usual suspects. Occasionally it would respond to the accelerator, but often wouldn't. It turned out to be a fault in the wiring loom which was eventually repaired expensively by a main stealer. Land Rover (or whoever made their wiring looms) in the 2000s obviously had a batch of wire with stiff, brittle conductors and insulation that tends to crumble and chafe. I've seen this kind of fault mentioned in a number of places online and even read about people replacing parts of the loom (from accelerator pedal to ECU) with lengths of multi-core trailer cable. In early 2015, as part of an attempt to deal with a persistent non-starting problem, I had a new loom fitted. It's really soft and supple compared to the old one. I hope it'll be a bit longer lasting.
So the moral of the story is, when trying to find the cause, don't forget the wiring loom itself.