There is a Lionel Frederick Symondson listed in the January to March 1899 birth index Steyning District, Sussex volume 2b page 282.

In the 1901 census living at 58 Warleigh Road Civil Parish Preston, Ecclesiastical parish of St Saviour, Brighton Sussex. Registration District Steyning, Sub registration district Shoreham.
Sydney F. Symondson age 38, born at Hounslow, Middlesex occupation coal merchant (employer).
Wife Wilhelmina age 36, born at Bedford Square, London.
Daughter Gertrude age 15, born at Hounslow, Middlesex,
son Sidney age 13, born at Hounslow,
daughter Wilhelmina age 12 born at Hounslow,
son Henry age 11 born at Hounslow,
daughter Barbara age 9 born at Hounslow,
son Robert age 7 born at Hounslow,
son Victor age 4 born at Hounslow,
son Lionel age 2 born at Brighton, Sussex.
They have 1 domestic servant. Visiting with them are his father Henry Symondson, mother Barbara Symondson, his brother Herbert and his family.

London School Admissions Plough Road School, Wandsworth
August 24, 1908, Lionel Symondson, father Fred [Sydney Frederick], 10 Huntsmoor Road, born December 13, 1900 [should be 1898], last School Infant School, left December 22, 1910.

In the 1911 census 1 St. Johns Hill Grove, Battersea SW, London
Sydney F. Simmonds, age 48, musician conductor, associated with a roller skating rink, employer, born Hounslow.
Wife Wilhelmina Simmonds, married 26 years, age 48, 10 children born alive all still living, born Holborn.
Daughter Constance Simmonds, single, age 22, musician roller skating rink, worker, born Hounslow. Son Robert Simmonds, single, age 17, Electrician Operator at Cinematograph Theatre, worker, born Hounslow.
Son Victor Simmonds, age 14, born Hounslow.
Son Lionel Simmonds, age 11, born Brighton, Sussex.
Daughter Phyllis Simmonds, age 9, born Brighton.
Son Ernest Simmonds, age 7, born Brighton.
The house had 7 rooms.
[Note most other family members are using the name Symondson in this census.]

WWI Medal Card
Lionel F. Symondson, Rifle Brigade, Regimental Number 46464
Victory Medal, British Medal
[12th Battalion Rifle Brigade]

In the 1919 Electoral Registers at 29 Solent Road, Hampstead and Holborn, Camden, London Lionel William Symondson [note the different middle name], Robert Alberto Symondson and Alfred Victor Symondson.

In the 1921 census The Grove Neasden Lane, Harlesden, Willesden, Middlesex
Head M. Robert Boss, age 49, married, born London, fine art dealer 9 Broten Street W.
Visitor Gertrude Emily Tonks, age 35, married, born Hounslow, Middlesex
Visitor Lionel Frederick Symondson, age 22 years 6 months, single, born Brighton, theatrical - no fixed place
Visitor Phyllis Marie Symondson, age 20, single, born Brighton, theatrical - no fixed place
Visitor Ernest William Symondson, age 17 years 7 months, single, born Brighton, theatrical - no fixed place

In the London Electoral Registers
124 Sutton Lane (West side), Feltham, Hounslow Heath Ward
Agnetta Symondson
Lionel F. Symondson

1939 England and Wales Register
100 Bulstrode Avenue, Heston and Isleworth, Middlesex
1. Lionel F. Symondson, born December 13 1898, married, collector - cash
2. Nita Symondson, born June 9 1899, married, unpaid domestic duties
3. Mary [later changed to Mary Anita] Symondson [later Hunter], born January 11 1927, single, at school
4. record officially closed

London Electoral Registers 1962
100 Bulstrode Avenue, Hounslow West, Heston and Isleworth
Agnitta [as spelled] Symondson
John R. L. Symondson
Lionel F. Symondson

In the Feb 1988 death index Lionel Frederick Symondson, born Dec 13 1898, age 89, Reading and Wokingham district, Berkshire.

Born at Preston Park, Brighton.

known as Nita

Agnetta and Lionel are first cousins with them having the same set of grandparents August Arnold and Emily Arnold (nee Irvine)

In the 1901 census Brunswick Cotts, Grove Road, Isleworth, Middlesex.
Head Albert W. Arnold, age 27, stonemason, born Hounslow, Middlesex.
Wife Rosa Emily Arnold, age 25, born Chatham, Kent.
Son George A. Arnold, age 5, born Hounslow.
Daughter Agnetta Arnold, age 1, born Hounslow.
Son Stewart Carl Arnold, age 5 weeks, born Hounslow.

[from Veronica Lisle ]In the 1911 census 42 Grove Road, Hounslow, Middlesex.
Head Albert Arnold, age 40, stone mason, worker, born Hounslow, Middlesex.
Wife Rosa Arnold, age 35, married 16 years, 5 children born alive all still living, birth location not given.
Son George Arnold, age 15, Post Office messenger, born Hounslow.
Daughter Agnetta Arnold, age 12, school, born Hounslow.
Son Stewart Arnold, age 10, school, born Hounslow.
Son Jack Arnold, age 8, school, born Hounslow,
Son Reginald Arnold, age 6 1/2, school, born Hounslow.
The house had 6 rooms.

In the 1921 census 42 Grove Road, Holloway, Isleworth, Hounslow, Middlesex
Head Albert Arnold, age 49 years 10 months, married, born Hounslow, Middlesex, stone mason
Wife Rosa Arnold, age 45 years 8 months, married, born Chatham, Kent, home duties
Son George Arnold, age 25 years 5 months, single, born Hounslow, postman -G.P.O. Twickenham
Daughter Agnetta Arnold, age 22 years, single, born Hounslow, stenographer, British Thomsa-Housta Co., 25 Bridge Row EC4
Son Stewart Arnold, age 20 years 4 months, single, born Hounslow, telegraphy - Eastern Telegraph, Electra House Finsbury ?????
Son Jack Arnold, age 18 years 5 months, single, born Hounslow, motor mechanic - E. C. Piercy, 255 High Street Hounslow
Son Reginald Arnold, age 16 years 7 months, single, born Hounslow, machine worker, Savory & Moores, New Bond Street, London
Boarder, [mother-in-law] Rosa Sharpley, age 75 years 11 months, widow, born Hounslow

In the April to June 1926 Marriage index is listed Agneta Arnold and Symondson. Willesden, Middlesex.

In the March 1998 death index, Agnetta Symondson, born June 9 1899, age 98, Reading and Wokingham district, Berkshire.