Thanks Mintalkin. Off to the doctors today for a full diagnosis. Will feed back what thye say.
The diagnosis, (having had a full check by a diesel specialist with full diagnostic equipment) is a faulty fuel pump - but, they are not 100% sure - so they are suggesting a £500 - 600 bill to maybe cure the problem. I really have no idea what to do for the best on this one, but seesm a bit steep for something uncertain.