Spoke too soon .. .. so just spent the last 2 hrs removing the intake manifold (again ..), finding the suspect ground wire on the fuel pressure sensor, cutting it out and soldering in a new wire, all heatshrinked. All put back, fires first time great - 15 mins later on a hot engine - no start again ...
Checked the 5v reference, ground and signal so know wiring is now good.
It's got to be the sensor itself - so have just bought a genuine Bosch one with the new insert and washer.
I'll do a DIY when it arrives as I know how to get the intake manifold off with my eyes closed now ..