Hello, just to update anyone that is searching this thread or has the same problem. I have had the problem for about 2 months now and tried the EGR
clean, glow plug check, cleaned every pipe / hose filter I could find plus disconnected the battery to see if it would force a re-set but to no avail. Still no apparent running problems. Just about to throw myself and my wallet at the mercy of a dealer.
Yesterday, started the car at the end of the day as usual, warning lights gone, turned off and re-started a few times and still no warning so presume all resolved, fingers crossed.
Whilst I'm happy it has gone would have liked to have known what or why! Bide my time until the next helpful light appears!