Thanks for your input. Clearly this is one of those problems that needs to be worried to death or until we trip over that one fault that is tripping everything else.
Not sure what the CSV file is or how to upload it, or indeed how to save it. I have tried a SD card into the Nanocom but it keeps refusing it. The problem may be in that the one card I have is 64G and too big or that my Apple Mac has formatted that card and the Nanocom seems to work off Microsoft Operating System? I did try to purchase a smaller card but 32G or 64G would appear to be the only card my supermarket would sell. Off to town tomorrow so possible a smaller card may help. I will format it, if that is required, on my old laptop which has a MS OP!
I was informed that the 'new' ECU came off a running vehicle, but...
I have looked at the old ECU and the conformal coating seems to be intact with no burning or damaged PCB tracks, but then I cannot get to the underside and I suspect that it is a three, or more, layered PCB. Quick look for a ECU repairer was £275 as a starting cost, more if the problem was severe! If I could find a new one then I would have purchase that. 20 / 20 hindsight is a wonderful thing!