Yes, Feb 9 1848 is the correct Mary. I am going to try for her now on the Census.
This still leaves Nell, my grandmother, born in May 1894 which would make her 16 at the time of the census. I know she was in service somewhere in Cheltenham at some point prior to the family moving to Crosskeys in Monmouthshire (where other children had already gone for work) but using any of her names has not brought up anything.
You have been a goldmine!!!