The one in front of the Spoonbill, too big for a Dunlin, Grey green legs
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Is it just me, isn't the spoonbill sighting a lot more interesting?!
If you enlarge the picture, you will see a straight bill, but longish also a white ring around neck, I have redone the photo
Although the bill may appear to be straight (probably due to the angle of the photograph) the bird in question is a Curlew. Greenshank is a smaller, slimmer bird - closer in size to the whiter bird on the right, which, although not clear, is not a Dunlin. This bird looks like a Grey Plover, although there is an outside possibility that it is a Knot.
I agree with RoyW that the wader on the left is a Curlew. The small bird on the right could be a Knot - it should be greyer and with less uniform upperparts if a Grey Plover.
Lat/Lng: 51.0, -4.2
OS grid ref: SS4933