Hello, I'm sorry nobody has replied to you sooner, I hope I can assist.
From the description you've given this may well be a common fuel pump concern. as the engine starts on easy start this confirms it's a fuel problem, although there is diesel at the injectors it won't be under the correct pressure or the correct amount.
Start by checking the following.
The fuel pump is powered by 2 fuses in the fuse box under the bonnet, F1.21 and F1.22, both are 20 amp and are at the top of the fuse box. At the pump connector pin 7 (red/black wire) is a 12 volt feed, you need to check this with the ignition on and the pump still connected as if you disconnect the pump the PCM detects this and cuts the power to it. Pin 6 (brown/yellow) is the pump earth, check the resistance of this to earth. Pins 1 and 2 of the pump are CAN wires, you need a scope to check these, also check the fuel pump wiring where it runs under the manifold near the engine to make sure it hasn't rubbed through. try disconnecting and reconnecting the pump connector as it's common for there to be a bad connection here.
The only certain way to confirm a fuel pump fault is to have a diagnostic scan carried out on the engine management and retrieve any codes stored in the memory usually the codes are for FIP requesting engine stop and a FIP malfunction, the codes stored are P1564, P1664 and P1665.
Check that there isn't any air getting into the fuel as this will cause fuel pump issues.
If it is the pump causing the problem a new pump is quite expensive so you would be better having your pump repaired, a good company that I've used previously is at http://www.ecutesting.com/bosch_vp44_diesel_pump_repairs.html but you need to remove the pump yourself to send to them.
Start with confirming if it is a pump concern, let me know if I can assist further or if you have more questions regarding this and I'll reply as soon as I'm able to.
Once again sorry you haven't had a reply sooner.