In the July to September 1907 birth index Charles William Symondson, Camberwell, London, volume 1d, page 790.

Parish Records St. Silas, Nunhead, Southwark, London
Born July 18 1907, baptism September 8 1907, Charles William Symondson, father John Charles Symondson, mother Gertrude Florence Symondson, [I can’t decipher the address], father is a book binder, ceremony performed by J. H. Hinchcliffe?

In the 1911 census 1 Arica Road, Brockley, Deptford, London S.E..
Visitor John Charles Symondson, age 28, vellum binder, out of work, born London.
Visitor Gertrude Florence Symondson, age 25, married 6 years, 1 child born alive and still living, born London.
Visitor Charles William Symondson, age 3, born London.

London electoral Registers 1931
13 Howden Street, Camberwell, Southwark
Charles William Symondson
Gertude Florence Symondson
John Charles Symondson

London electoral Registers 1934, 1939
13 Howden Street, Camberwell, Southwark
Charles William Symondson
Gertude Florence Symondson

Since Charles William Symondson is listed in the Electoral Registers at 13 Howden Street with his mother before and after WWII, but not in the 1939 England and Wales Register, I believe the Charles William Symondson in the Pioneer Corps is most likely this family member.
London Gazette, July 30 1943
The undermentioned cadets to be 2nd Lieutenants
Pioneer Corps
16th May 1943
Charles William Symondson 284597
and
London Gazette, April 7 1944
Regular Army
Emergency Commissions
The undermentioned War Subs. Lieutenants to be War Subs. Lieutenants, retaining their present seniority
31st December 1943
C. W. Symondson 284597

London electoral Registers 1945
13 Howden Street, Camberwell, Southwark
Charles William Symondson

In the April to June 1946 marriage index Charles W. Symondson and Olga U. Reavenall, Brentford, Middlesex, volume 3a, page 816

London electoral Registers 1952, 1953
13 Howden Street, Camberwell, Southwark
Charles William Symondson
Gertude Florence Symondson
Olga U. Symondson

In the March 1985 death index Charles William Symondson, born July 18, 1907, age 77, Worthing, West Sussex, volume 18, page 3037.

National Probate Calendar
Charles William Symondson of Seaview Court Rowlands Road Worthing died 28 March 1985 Probate Brighton 4 June 1985.

In the January to March 1913 birth index Olga U. Reavenall, Leicester, Leicestershire, volume 7a, page 454, mother’s maiden name Rowe.

1939 England and Wales Register
11 Byron Road, Ealing, Middlesex
1. Freda M. Reavenall, born January 31 1911, single, wages clerk newspaper
2. Olga U. Reavenall, born January 20, 1913, single, ledger clerk drapery
3. Nellie Reavenall born July 11 1884, married, unpaid domestic duties
4. Clifford J. Saunders, born October 23, 1910, single, chartered Lec. acting as chief accountant to manufacturing company

London Electoral Registers 1939
11 Byron Road, Mount Park, Ealing
Nellie Reavenall
Freda May Reavenall
Olga Ursula Reavenall

In the March 1998 death index Olga Ursula Symondson, born January 20 1913, died age 85 Worthing, West Sussex, register 4B16C, district 7864B