The Ford Transit does not carry heating, the reason for the starting failure can be sympleously that the injection pump is discharged (quite frequent fault in Ford) by air entrance to the diesel pipes through the rapid plugs.
To know if that is or not, just park it downhill in a pronounced slope. If the next morning it starts the first and yet in doing so uphill, it does not start, it is a symptom that the tubes are discharged and the pump injects the little it has inside the same pump and fails until the diesel goes up again from the tank.
Another way of seeing it is taking out the arrival and exit tubes of gasoleum to the pump and putting a carafe high, purges the circuit, starts and the paras, leaves it with the carafe up all night and if in the morning it does not fail it is because the pump has not been downloaded (because the hook is higher than the gas pump).
The solution to this problem is to replace the rapid plugs with spikes with a clamp (of those of a lifetime) and put an anti -background valve in the suction tube of the injection pump so that it is not discharged.
Another cause of this type of breakdown is the lack of engine compression due to wear and mileage, if it has been failing to start, it pulls blue smoke and lacks the engine, it is possible that it is because it is low compression.
My advice, (that in that I do agree with the rest) take it to the workshop and look at you, and if it is a workshop specialized in diesel injection better than better.
All the best.