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The bird in question is a juvenile Dunlin (which has just started to moult into its 1st winter plumage).
The most obvious feature which identifies it as this species rather than a Curlew Sandpiper is the fairly extensive black spotting on the underparts - this is restricted to, at most, the sides of the upper breast on Curlew Sandpiper. The supercilium (pale stripe over the eye) would also be more distinct, and probably visibly split into two, if it was a Curlew Sandpiper.
The bird to the right may be a juvenile Little Ringed Plover (Charadrius dubius)because there does not appear to be any obvious white above the eye - the image is not clear enough to safely eliminate a juvenile Ringed Plover (Charadrius hiaticula) though.
Lat/Lng: 52.855832, 0.445935
OS grid ref: TF647315