The tdi landrover engines which use Bosch pumps will run fine with Veg oil in the warmer months, but pre tdi engines with lucas pumps its not recomended.
For the winter a weaker mix of veg oil or pre heating is required. The best systems start and stop on diesel and use heated veg oil for the rest of the trip.
Grasshopper,
If the P38a is a pig to start when hot, its not usually the injectors at fault, its the pump. When hot and left standing the fuel in the pump gets hot and alters the viscosity, which the pump cannot handle. The trick is to carry a bottle of water and soak the pump, cooling it and then it will usually start. ;-)