Charadrius - hiaticula vs psammadrama

Races are not everybody's cup of tea I know, but finding out where birds come from and where they are going to must surely interest most. Over the last few days on the Dyfi Estuary and today at Fort Belan has given plenty of opportunity to look closely at Ringed Plovers. The two races that we get here in North Wales are really quite distinctive and at this time of year and again in autumn gives us an opportunity to see both races of Ringed Plover side by side. Our local breeders, the nominate race Charadrius hiaticula are a common sight breeding on shingle beaches and  ridges, while the northern race 'psammadrama' is regular as it passes north in spring and south during the autumn.
 From what I have read-up on and put into practice over the past weeks, these are the main ways of seperating the two:

Charadrius hiaticula - the nominate race and our local breeders (top bird in photos):-
- larger bird overall and more 'plump' in appearance.
- body appears more 'round' folding wings appearing shorter.
- upperpart feathering paler than 'northern' birds - a buff brown.
- black breast band and face patterning are jet black in breeding plumage and appear clear cut.
- moult pattern is different. Undergo moult on breeding grounds so at the moment flight feathers look very worn (note the sgraggy coverts in the photo above)
- lumbersome in movement, taking its time getting from one place to another.

Charadrius psammadrama - the northern race breeding in northern Scandanavia. This race was formerly known 'tundrae', however 'tundrae' is now used to refer to birds breeding further east again.
- smaller bird altogether and looks 'sleeker' in appearance
- body looks more slimline, with long looking folded wings.
- upperpart feathering appearing darker than nominate birds - brown as opposed to buff.
- breast band and head pattern not appearing as clean cut at this time of year and black is less likely to be jet black.
- moult pattern different - undergo a complete moult on their wintering grounds (western Africa) so their flight feathers appear fresh and clean looking (this can be seen in the bird in the lower picture above, taken today)
- often dashing about a bit like a calidris wader. Seemingly quicker in its movements.

However, not all birds are this simple and there are some birds where I'm not sure - seemingly smaller and dark but with 'hiaticula' moult... Fresh looking paler birds.... is there such a thing as intermediates?

And what about this one below? - naff picture but quite obviously the head patterning of a young bird - a presumed 2cy bird as the upperparts didn't appear scaly as an early juvenile would show. This was the only one in this plumage out of 550+ Ringed Plovers present!

Shouldn't the first breeding plumage of a Ringed Plover be as a result of first pre-breeding season moult? Shouldn't this occur a long time before June?  Any wader moult experts out there? (Note the adult ' hiaticula' bird to the right with its worn flight feathers).

And then there's Semi-palmated Plover of course ;-) Knowing our Ringed Plovers will help nail one of those.........the challenge is set!