Sc will start after much head scratching (and trawling through the internet) I decided to go back to the basics. First ensure battery is fully charged (put it on charge for several hours) this gave time to check everything fuel fuel filter glow plugs air leaks vacuum pipes etc. Tried starting again fires up first time and running as normal, conclusion new battery required, sub zero weather will kill poor batteries voltage drop when cranking must interfere with sensitive electronics, sensors etc resulting in failure to start. This could have been very expensive if one starts replacing components that are OK or employing so called expert services . Hope this helps anyone with same symptoms .
With luck we live and learn