My mother came to England on a domestic permit in Sept 1938. I have been doing research on this topic and have been trying to to see what one of these permits looks like for more than 5 years now with no success. So, if you find one please let me know.
There has been quite of bit of research done on Austrian women who fled Vienna and came to England as domestics. A leading researcher in this field in Tony Kutschner. The Association of Jewish Refugees in London is a good source of information on the women who came to the UK as domestics. A complete book on the subject has been written by Traude Bollauf.
Let me know if you would like to discuss this in further detail.