In the 1841 census
Henry Symondson age 38, pianoforte ma [maker].
Wife Teresa age 40. Son Alfred age 10,
son Henry age 9,
son Frederick age 7,
daughter Louisa age 5,
son? Teresa age 3.
All were born in the county of Middlesex. Civil parish St Pancras, Hundred Ossulstone (Holborn Division), Middlesex, Registration district St Pancras, sub registration district Regents Park. Living on Robert Street.

Listed in the 1851 census Address 3 Dean Street Civil parish Westminster St Margaret, ecclesiastical parish Westminster, Middlesex, England. Registration District Westminster, sub registration district St Margaret.
Theresa Symondson (or Symonson) widow, head, stationer, age 51, born in London. Son Henry Symondson age 18, born in London, occupation Music Seller.
Son Frederick Symondson age 17, born London, occupation Music Seller.
Daughter Therese Symondson, age 13, scholar, born London.
Daughter Marcella Symondson, age 9, scholar, born London.
[3 other families lived at this address as well, presumably on different floors.There are 5 floors today. I imagine their shop was on the ground floor and they lived above.]
[3 Dean Street is now a Tesco Store with address 2 to 4 Dean Street. Near Oxford Street.]
[Historical Note: Karl Marx (listed as Charles Mark) and his family were living at 28 Dean Street from 1851 to 1856]

Listed in the April to June 1852 Death Index. Teresa Symondson, Westminster, St Margaret, Middlesex, volume 1a page 179.