Thanks for the reply AM. The message popped up when I was on a long run as it happens; but your point about fuel is interesting. I'd started the journey with a tank of Shell plus but the two refills in Spain have been with some cheaper brand. Is there a chance the message might clear with a top up of a BP premium brand which I have seen local to where I am?
They usually clear after so many starts as long as the fault isn’t continuous. Usually it logs it going out of range for only milliseconds. It’s not so much a long run as a hard run. It needs lots of pressure to force the soot out. It means getting it right up to normal temp and driving it at high revs (not on the rev limiter) by holding it in a low gear. You need to take care and mind no to speed - a low gear up a steep hill is best. You will also be able to clear the code by disconnecting the battery earth cable for a few seconds but make sure the ignition is off, all the windows and sunroof if you have one are shut and the key is in your pocket otherwise you might have to start initialising things. The best way is with a code reader. They cost £20-£30 here and you can clear codes. I can tell you how to do a forced regen but it’s quite scary because it will rev it’s nuts off unattended for about 20 minutes but I’d rather not post it as folk shouldn’t be doing it willy nilly. Pm me your email address if you cannot clear it any other way.
As for fuel, branded regular diesel has more additives than supermarket diesel and high grade diesel has a double dose. These detergents help to clean the pump, injectors and reduce carbon build up. I’m not sure how long it would take to clear carbon after it’s been formed. I would try clearing the code first to see if it comes back. You would do well to stay away from supermarket fuel on a permanent basis (the critics will argue otherwise but they aren’t the ones stuck). A can of BG244 from Amazon every 12 months is also a good idea.