Hellyer Group - Figuring Them Out

For this to fit it has to be summer/fall 1927 at the latest.
Were women wearing shorts this short in England in the 20s?
I previously thought this was the mid thirties although the dresses do look earlier, I suppose.
Any possibility someone could ID the background car?

Back row, L to R: Kate (Hellyer) Robinson, Marie Rose (Hellyer) Gregory, Jane Hellyer (Jane Major Davey Hellyer) "The Mother" , and Millicent (Maud) (Hellyer) Earp
Front Row: (Possibly) Frank Hellyer's wife (Florence? Sylvia?) Frank Hellyer, Margaret Constance Hellyer, Arthur Sydney Hellyer.

(Arthur) Syd m Sadie (Sarah Graham) in 1916 Bethnal Green
Frank married Sylvia Morley, St. Olave 1927? OR was it Florence Cleal?

Syd and Sadie's kids:
Sydney G. Hellyer born 1917 Tynemouth d. 1985
Frank E. Hellyer born in 1920 Tynemouth d.1983
Joyce Hellyer born 1926 Tynemouth d. 2002

Jane died in Oct - Dec. 1927 at 73.
Arthur (known as Syd) died in 1933, age 42

Possible correction: I think Frank is Frank E. Hellyer who married Florence Cleal in Kent, Apr - June in 1923. Or maybe not.
If it's the Sylvia/Frank one - they had a girl, Sylvia in 1928 and a boy, Peter, in 1934.
If it's the Florence/Frank one, they had Brenda in 1929 and Maureen in 1931.

In this photo Syd would be about 36 and Frank would be about 32.
And Florence would be about?