Geof I do keep looking at the Robert Hewitt you found but Sarah was born in Workington, and the spelling is off- which I knw doesn't mean anything. I have an address that her father lived at in 1923, 94 Corporation Rd. most of the names match up to the ones I've heard. I did go ahead and order the birth certificate for the 1877 date and one for 1880 that I found- gma seems to have had quite a few different years in which she was born and 1877 would have made her about 40 when she had my mother. Her parents were married in Gretna Green, I found a second cousin who went to England a few years ago and met a lot of the family and confirmed the stories were true- some still live in Penny bridge. But thank you for the trouble of looking this up.
You have information that Sarah
thought she was born in Workington. The birthplace of brother George shows that she was living in Workington by the time she was aged 6 - possibly sooner. She need not have known exactly where she was born.
There is little doubt that in the family I found in 1891 the mother's maiden name was MARRS - the son's middle name surely confirms this. I would have thought the name MARRS was close enough to MAYS to make it a possibility.
There were two (and only two) HEWITTs with forename Robert in Workington according to the 1911 census index one was aged 57 and born in Brampton the other was George Robert born in Workington. Surely the ones I had found in 1891.
Unless you can find evidence, a family story that her parents married in Gretna remains just that - a story. I can't find the marriage here
http://www.achievements.co.uk/services/gretna/index.phpYou can dismiss this family totally. The father Robert, the sister (Mary) Agnes, the brother George Robert, Mary MARRS instead of Mary MAYS. Then you have to try and find another Robert HEWITT with children called Agnes, Sarah, George Robert who lived in Workington. There were several Mary MARRS in Cumberland but not a single Mary MAYS.
It all boils down to a balance of probabilities.

There were lots of siblings for Sarah in 1901
Sarah 23, Mary Agnes 21, George R 17, John 14, Henry M 12, Ann B 9, Emily M 4, Mabel under 1month.