Here are some Austin images that gives you an idea of what was used over the years.
The block Austin letters as used under the red Flying A was used from 1947 through to British Leyland days. The BMC Rosette as per the one below and the one at the All British Day (shown in the separaet article and on the home page of the website) was the Australian version - the British one was more complicated and used yellow as well. The Austin Coat of Arms was also used from the late ‘40s through to about 1970. The Austin script as used on the grille of the 1800 was never used in print as far as I know.