Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 149,270 pages of information and 234,239 images on early companies, their products and the people who designed and built them.
Sunbeam Motor Car Company of Wolverhampton was a manufacturer of cars, buses and engines. They also built aircraft during WW1. For description of Sunbeam bicycles and motorcycles see John Marston Ltd.
See also -
1899 The first Sunbeam motor-car was built by John Marston Ltd
1905 January. The Sunbeam Motor Car Company Ltd was formed to focus on car production of John Marston Ltd, as distinct from its interests in the production of cycles The first directors were John Marston, Edward Deanesly, Samuel Bayliss, Thomas Cureton, Henry James Bath and Herbert Dignasse.
1914 Increased demand for Sunbeam cars due to the work done by the Sunbeam racers in France; first engines made for aircraft
1918 was a very tragic year for the Marston family. Firstly, the eldest son died, followed by his father the day after the funeral and his mother a few days later. It was to affect the firm deeply.
1918. AGM. Thomas Cureton is Chairman; Charles N. Wright appointed new director on the recent death of John Marston. Other directors re-elected are Henry J. Bath and L. Waterlen. Louis Coatalen mentioned as involved in the technical design. 
1919 Raised addition capital of £350,000. Makers of the Sunbeam car and the Sunbeam-Coatalen aero-engine. Directors: Thomas Cureton (Chairman), H. J. Bath, Samuel Bayliss, Louis Coatalen, Edward Deanesly, Charles N. Wright and W. M. Iliff (MD). 
c.1920 Facing a claim for death duties arising from the death of his father, Charles Marston sold his shares in John Marston Ltd. The company entered the new decade in the control of others, John Marston Ltd being acquired by Kynoch, part of Nobel Industries, in 1920.
1924 Dario Resta was killed at Brooklands driving a Sunbeam GP car.
1927 The Moorfield Road site was now some thirty acres and the company employed around 4,000 people.
Late 1920s: began development of an electric trolley bus design - see Sunbeam Trolleybuses
1929 Introduced a 45 h.p. six-wheel chassis for double-deck omnibus. 
1933 H. C. Stevens designed the 'Dawn' which appeared at the Motor Show. This was a lower cost model with a 12.9 hp four-cylinder engine
1936 Re-branded as Sunbeam-Talbot both now part of Rootes