Thought I would post this as it may help someone.
My TD5 was suffering from intermitant starting and every check we made drew a blank,whilst changing the starter motor it was noticed that the sensor plug had been repaired,strange as we recently changed the sensor and it was ok then.
The sensor wires had been soldered back at the plug and covered with shrink wrap not very well and the two wires were loose causing the problem,new cable and all is well.
Seems that that the wires were pulled out when I had a new clutch fitted and our troubles began.