I have found something possibly interesting (all from
http://www.freebmd.org.uk )
Ernest Hawthorn m. Harriet E Reeves 1913 in Hull
several children born
Ernest Hawthorn d. 1922 aged 32 in Hull
Harriet E. Hawthorn m. Herbert
Swatman 1929 in Hull
Harriet E Swatman d. 1935 in Sculcoates (possibly due to complications in the birth of Iris Swatman b. and d. 1935)
Herbert Swatman d. 1944 in Hull
Between the 1922 death of Ernest and the 1929 remarriage, there were two daughters born who are registered under the surname "Hawthorn", mother's maiden name Reeves, but with middle initial "S". I believe the girl born as E.D.S. Hawthorn is your Ethel Doreen Swatman.
Her father was almost certainly Herbert and the birth certificate will probably show her with a middle name "Swatman". I would presume that she was raised using that name, dropping "Hawthorn".