UPDATE fixed
had ecm tested no fault found so back to the \drawing board/ started with dead basics ie battery connections onwards, at this stage still same symptoms eng start and run then cut dead.
at this stage had a stroke of good fortune or (divine intervntion?) after eng had stopped and was refusing to start my colleague was fiddling with the fuse box connections and lo and behold eng now fired up. on closer investigation we noticed on pressing down on the torx screw at the rh hand rear of a main connection which felt tight and then letting go the eng could be made to run and not run depending on pressure applied, we then removed fusebox and inspected fully and resecured a caged nut and rebuilt,the eng now kept running irrespective of pressure applied.
i assume this had temporally been not allowing a feed to supply side of pressure regulating valve plus other components which not allow valve to close and thus no fuel pressure to build up in fuel rail.
the customer has now had vehicle back 4 days and at moment i have all my fingers and toes crossed.
GEOFF.