On the way to work this morning, I noticed I was really down on power - no turbo whatsoever!.
I called my Dad (who has a 1.9TDi Avant) and he said that he occasionally had the same problem, which was usually sorted by switching off the engine and restarting.
I did the same, and the problem seems to have cleared.
Is this a common occurance, and what (if anything) can be done to rectify what I see as a potential future problem of the same sort?
Many many thanks once again in anticipation.