I had the same problem summer time.It started with a suden engine cut off. Right after the first engine cut off it took longer to get it started. It would normally start in 2 secconds when I turn the key. But after the engine cut off it took like 10 or more secconds when I turned the key.

After a short while it refused to start completely. It would only start with help of easy start. It would also cut off while I was doing 60-65mph on the motorway. I had to switch off the ignition and turn it back on again while I was still travelling at that speed.

I made a mistake of taknig it to my usual garage. They said it is the crank shaft sensor, changed it did not cure it. Than they said it is the little silinder thing on the fuel pump ( i cannot remember the name) changed it nothing. Than they said it is the fuel pump changed it with a seccond hand one and still nothing. Doing all those took more than a week. Than I needed the van took it and started to use it with easy start.

A month and 1000miles later I took my van to a diesel specialist. I live in north west london so I found a diesel specialist in uxbridge and went there. Connect their computer to the van and said rail preasure. It ment one of the injectors was gone. Than he plugged bottles on each injector, one of them was throwing fuel back at the botle. Changed the injector good as new. Their price a bit steep but get they job done. It cost me £72 to check it with computer, £40 for the bottle test, £125 for reconditioned injector £72 for fitting the injector and all plus VAT. It cost around £400 but get it done at the end. It took les than 2 hours to get it fixed.