We have a 2.0hdi, 181,200 miles, 2000. Drives faultlessly
apart from occasionally cutting out 
. Has happened three times so far. 1) First time was 15 June, 180,200 miles at 30mph, travelling down a slight slope on a straight road, about 10 minutes after starting off. The car just cut out, and would not re-start. The engine management light came on. It was recovered to our house, and on the following day did start, although the engine management light remained on. The garage were unable to find any useful information using their fault code reader.
2) Second time was on the 26 June, again at 30mph, just after a roundabout, about an hour and 50 miles after starting off. The car just cut out, and would not immediately re-start. The engine management light came on. After about 20 minutes the car did start, although the engine management light remained on. It drove 3 miles to the immediate destination, then stayed there for 4 or five hours. It made a further very short trip, then the 50 mile trip home, still with the engine management light on. The garage were unable to find any useful information using their fault code reader, however the did find very low pressures in the high pressure pump, and next to no fuel returning to the tank in the leak off pipes. They therefore changed (ouch!) the high pressure pump and (since it was due anyway, and needed to be removed to change the pump) the timing belt.
3) Third time was on 08 August, again at 30 mph, on straight level road. Car had driven 50 miles in morning successfully, then been parked for 4 hours. It cut out about five miles into the return trip. The engine management light came on. It would not immediately re-start but after only about three minutes it did start, although the engine management light remained on. It drove the 45 miles home, still with the engine management light on. The garage were unable to find any useful information using their fault code reader but took it for some trips (total 25 miles) with their laptop monitoring it - everything checked out as fine with no problems.
Since then we have driven 150 miles without problem, however we no longer have confidence that the car will keep running. The garage suggest perhaps a sensor fault, or maybe a wiring fault, but they admit to being pretty much in the dark. Neither they nor I am keen to diagnose by random part replacement.
Any suggestions anyone, for how we can diagnose the problem?
Regards
Simon
) I didn't really want to mention it, as you say it's better to diagnose the problem than keep bunging cash at it. 
I followed the wire down from the sensor as it disappears down in front of the block and there I found a connector just dangling about, just like yours, and then it goes in the plastic trunking with the rest of the wiring. I reckon it came from the round plastic thing in the hole in the crankcase to the right. Another job for a cable tie I reckon, and I only had it in the air yesterday 
