Possibly a little grebe but difficult to ID.
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Just not at all possible to offer an ID, but you might be right.
My Flickr photos...
Not a long-tailed duck? The head looks pale with dark on the cheeks. Little grebe does not have a white crown.
Black guillemot is a thought I had too, but I still prefer long-tailed duck.
Oh for a little more sharpness. The head-shape and white crown/nape looks perhaps a bit more Long-tailed Duck than Tystie, but that white patch (apparently) on the wing had me swinging more for the latter. Agree though that I should perhaps have taken more note of the dark cheeks!
Flickr pics: http://www.flickr.com/photos/72243477@N00/
Lat/Lng: 57.222082933351, -5.6745457649231
OS grid ref: NG782205