The bird in my opinion is a nonbreeding-plumaged male (most likely first-summer) WESTERN SANDPIPER, based mainly on the structure of the bird, and supporting characters of plumage state and wear and the bill length.
''DETAILED DESCRIPTION (obtained when the bird was roosting with 22 summer-plumaged Dunlin at 5-10 feet range just above the high water mark)
The bird is part of a 64-strong flock of waders currently residing on Dawlish Warren beach, including 21 Sanderling, 5 Ringed Plovers, 5 Grey/Black-bellied Plovers, 32 Dunlin and a single Little Stint. It is markedly smaller than Dunlin but slightly larger than Little Stint and easily picked out from the Dunlin (with which it feeds and roosts) by its drab, predominantly grey 'winter-type' plumage.
The structure of the bird is characteristic, with an overweighted, chest-heavy body structure and a noticeably thick neck. It has a distinctive white supercilium, petering out just behind the eye, and overall, grey (greyish-brown at very close quarters) upperparts. The lower underparts are completely gleaming white, with an obvious 'bracelet' of small streaks forming a broken 'breast-band'. A very few very light streaks extend on to the fore-flanks on both sides.
The mantle and upperwing coverts are uniformly marked grey, with each feather having a dark shaft-streak and pointed towards the tip. There is no hint of any warmth (rufous/chestnut) in any of the feathers. The crown is a shade darker than the rest of the upperparts, furrowed with darker pigmented and slightly blacker feathers. The ear-covert patch is distinctly darker in shade.
The primaries extend to just beyond the tail tip, whilst the secondaries are very frayed and worn
The all-black bill has a moderately thick base and fine tapered tip and lacks the distinctive 'blob-ended' tip that many Semipalmated Sandpipers appear to show. The legs are dark but slimmer than Dunlins and a tad paler, with partial webbing between the toes (confirmed by John Fortey's images and video).
In flight, a white wing-bar was apparent. Unfortunately, no flight calls were heard''
I received some excellent feedback on the identification of this bird from North America and I would very much like to thank Kevin Karlson, Julian Hough, Erik Johnson amongst others for taking the time to contribute to this very intriguing identification puzzle. I would also like to thank Killian Mullarney for his input, as well as Mashuq Ahmad, Mark Bailey, Dave Stone, Kevin Rylands, John Fortey and Ivan Lakin. I have added Kevin Karlson's comments on my Rare Bird Alert blog.
Once again, thanks to all of you that took the time to get involved - it is very much appreciated - and if you have further comments to make, I am more than happy to hear them.