I bought this unlabelled Dendrobium today at the International Orchid Show, Malvern, UK (see attached picture). The vendor couldn't remember its name but thought it might be a nobile hybrid; I can't see any nobile in it though. The flowers are 4-5cm across and it was faintly scented at 6pm.
Agree on a Dendrobium unicum hybrid. D. Chinsai, D. Yellow Chinsai, D. Pixie Charm are some other possibilities, along with D. Stardust, and probably others. All are some combination of D. unicum and D. moniliforme, and maybe something else, so all are rather similar.
Thanks for helping! I went to the Malvern show for the second day and revisited the vendor with the intention of jogging his memory with your suggestions...but he had remembered that it is Dendrobium Stardust 'Chiyomi'. According to www dot hortusorchis dot org/en/hybrid-orchids/136-d/1897-dendrobium-stardust-chiyomi dot html, it's one-eighth nobile, which shows how much I know. (Sorry about the munged URL, the editor won't let me include a proper URL for some reason).