Thanks to the wonderful 'Downton Abbey' wikia, here's what we know about Beryl Patmore:
Beryl mentions having two sisters, one who died prior to 1912 and another, Kate Philpotts, who is her nephew Archibald's mother.
She may have been born somewhere between 1869 or 1870.
In the 2013 Christmas Special, Mrs Patmore mentions that no-one "has wanted to squire [me] since the Diamond Jubilee". Queen Victoria's Diamond Jubilee was on the 20th June 1887 and Mrs Patmore had to have had her season (though she would not get a debutante ball due to being a commoner) by that time. A woman typically has her season when she is 17 or 18. Going by the ages of a woman having her season and Queen Victoria's Diamond Jubilee, Mrs Patmore would have been born in 1869 or 1870.
If it is true that Mrs. Patmore was never married and that her status as "Mrs." is an honorific based on her job in the Crawley family household, then it's pozz'ble, just pozz'ble, that she was from the Hertfordshire area as that is the source for that surname.
When Beryl was about 22 years old, I believe her parents came to London to visit her in the early months of 1892, before she had found employment in Yorkshire at Downton Abbey. I think the more... decadent side of life in the "Great Wen", the "Big Smoke" (both nicknames of London), was a bit more than Mrs. Patmore expected and she took a dim view of those who reveled in the brazen openness of their lifestyles.
Here's why I think this to be the case: I believe this was a quick shot of the Patmores as they walked the city streets. Mrs. Patmore is casting a VERY disapproving glance at Dorian Gray and his companion, the exotic Angelique.
This theory of relateeveety is dedicated to one of my bestest friends, Ivy Hurley, who is a big fan of both 'Downton Abbey' and 'Penny Dreadful'.
Happy birthday, Ivy!