Phryne's Toilette - Phryne's Bath Products and Soaps

Phryne uses a number of different toiletries throughout the books but here are they main ones mentioned.

Egyptian asses milk bath as used by Cleopatra:
It was purported the Cleopatra bath in asses milk to keep her young and beautiful. In the 1920's people had a fascination with ancient Egypt so i'm sure this information would have come to light and companies making beauty products may have exploited that.

Floris:
Phryne uses a number of scents from Floris including tea rose and honeysuckle. Floris is the oldest English retailer of toiletries and accessories and second oldest in the world. Floris was founded in 1730 by Juan Famenias Floris, who arrived in England from his native island of Menorca to seek his fortune. Shortly after his arrival, in 1730, he secured premises in Jermyn Street, in the elegant quarter of London's St. James's where the shop still is today.

Rose de Gueldy:
Gueldy was established in 1905 by Lelaurin and A. Sergent at 370 rue du Faubourg-Saint-Honore in Paris. Gueldy. Inc., aso operated at 21 East 40th St.. New York. Gueldy released La Rose in 1919

Facial Youth face cream:

Castile soap double milled scented with freesias:
Dr. Hunter's castile soapis  same all-purpose Olive Oil soap Caswell-Massey has been making since 1861. This is most likely the soap Phryne mentions.