Brian, my own first thought was that the 'Mrs Astor' listed is probably Nancy Langhorne Astor, mistress of Cliveden and future M.P. Her husband, Waldorf, would not inherit his father's title until 1919. Then again, it
could conceivably be Ava Willing Astor, since she was most certainly knocking around in London Society at that date and even made an appearance at court during the same summer season.
'Lady Curzon' is not the viceroy's wife, Mary Leiter, since she had died back in 1906. Instead, she is a different Mary, Viscountess Curzon and future Countess Howe, who was a celebrated beauty in her own right. Here she is pictured with Lord Lascelles at Ascot in 1913:
http://www.jamd.com/image/g/3425665
The Hon Victoria Sackville-West (or 'Vita' as she was, and remains, more commonly known) was very shortly to wed the diplomat, writer and diarist, Harold Nicholson, a highly tempestuous union chronicled in their son Nigel's book,
Portrait of a Marriage. During the Great War, and into the Twenties and Thirties, Vita would have lesbian affairs with Alice Keppel's daughter, Violet Trefusis, and author Virginia Woolf. Her novel,
The Edwardians, which was first published in 1930, is the very best fictional depiction of life in English high society prior to 1914, narrated by one who had an intimate first-hand knowledge of it.
Lady Desborough was one of the period's great hostesses, a prominent member of the Souls, and mother of two sons, Billy and Julian, both of whom would be killed fighting in 1915. Her third and only surviving son would die in a car crash in 1926. Her long and fascinating career was examined in one of last year's best biographies,
Ettie: The Intimate Life and Dauntless Spirit of Lady Desborough by Richard Davenport-Hines:
http://www.amazon.co.uk/Ettie-Intimate-Dauntless-Spirit-Desborough/dp/0297851748
Ettie's husband, first and only Lord Desborough, played an important role in bringing the Olympic Games to London in 1908 and was a friend of Sir Cosmo Duff Gordon (the two men were on the British fencing team together).
Another name worthy of note is that of the Countess of Lytton. She had been the beautiful Pamela Plowden and was the first great love of Winston Churchill, before he married Clementine Hozier. She and Nancy Astor are pictured together at a costume ball in 1910 in the new biography of Lady Desborough I've mentioned above. All three women knew one another and shared a rather uneasy relationship.
Lastly, I'd pick up on Sybil Sassoon, yet another ravishing beauty, and the product of a marriage between two of the great Jewish banking dynasties, Rothschild as well as Sassoon. She married the very handsome Lord Rocksavage in 1913 and eventually became Marchioness of Cholmondeley and chatelaine of one of England's greatest stately homes, Houghton Hall in Norfolk. She was very memorably painted by John Singer Sargent:
http://en.wikipedia.org/wiki/Sybil_Sassoon