Ahhh, it appears that I have had a senior moment. I do all my post processing on layers and add a 'snapshot' layer at various intervals, and I think that when I saved this image for the web, I didn't have all the layers activated. I have now uploaded the correct image which has the white line removed, so if your reading the above comments after I posted this, they were not mistaken or wrong.
LaFoto: The full file is somewhat larger (approx 12000 pixels across) as I merged three images to create this one result. The white line was caused because I used the pen tool to select the sky and then feathered the selection by 2 pixels before adjusting the levels and curves. I then used the same selection and inverted it to adjust the other parts of the image separately, and the overlap of the feathered edges allowed the original sky to show through. A little fine-tuning of the adjustment layer masks gets rid of it, as you can now see in the correct image above.
The sky was kind of washed out and grey on the day in question, and so I exposed for the ground intending to use levels and selective colour adjustment on the sky to bring out what detail was there.
Archangel: I didn't know you were from one of my favourite parts of the country. I tend to get away down to Devon at least two or three times a year, avoiding the tourist/school holiday season wherever possible. The original images had a dozen or so people on the harbour wall, but the clone tool

soon put pay to them. The sky is the one I shot, with the explanations as above. In fact my first post on this site included an image from the same trip -
Saunton. The hercules transport that was landing on the beach at the time is just to the left of the shot.
Mentos_007: Please you like the image, and apologies for my oversight in uploading the wrong image.
Apologies.
David