The car has been at the local diesel specialist now for five days - In that time, they have found and refitted a hose that had blown off the back of the engine somewhere which made a difference in as much as the car will now tick over.
Stripped and cleaned the EGR valve, made no difference.
Replaced the MAF with a known working one, made no difference.
Cleaned out the DPF ( not sure how, mind ), made quite a bit of difference, but, the car is still not "right" according to the garage.
Seems to have boost pressure, but, engine doesn't seem to respond to it. I have suggested Fueling, and also suggested that maybe the turbo needs to come off for a clean.
I have also suggested that some Vauxhalls with this engine have suffered burst intercoolers.
I wait in hope !