Today I spoke to the supplier about the cracked injector. They were really good, they said that the crack was due to an inherent casting fault and the refurbishers should have spotted it. It could not have been caused by an installation error. Thus there was no doubt about fault and they exchanged it straight away.
I fitted the replacement injector and she started up fine, with a lot less smoke. It only took about ten minutes to pop it in where the cracked one had been, bleed to pipe and start her up. So by early afternoon GB was ready to go. It was just a shame that it took me 3 hours to drive there and back to get the thing. Look on the bright side, one has to find something to do in retirement and what can be better than driving up and down the M1? Now I really must wash this diesel off me and my clothes.