Did you order the birth cert for 1917 Frederick J Penfold born in Croydon, mother's maiden name Lawrence?
I wonder if Phyllis knew TFP BEFORE she married Stephen Saunter.
Had child No.1 Frederick J. [with TFP perhaps)
Married Stephen and had 4 children with him.
Vera Vivienne Rhoda Saunter b.1922 Cranbrook, she married Cyril Seymour Huggett - they lived in Kent.
Her story is on the BBC website
http://www.bbc.co.uk/ww2peopleswar/stories/40/a2989740.shtmlStanley Stephen Saunter b.25 May 1923 Cranbrook d.Dec 1998 Mansfield Notts, he was married.
Peggy Vivan Saunter b.10 Jul 1924 East Ashford d. Feb 2004 Staffordshire, she married Alexr Rankin in 1943.
Rudolph F P Saunter b.1927 East Ashford, and I can't find any sign of him. He was very young, and perhaps also adopted out with a name change in the process.
Then Phyllis gets back with TFP and 3 more children arrive in quick succession, bringing the total to 8.
Quite a handful, and if TFP then jumped ship or either was taken ill for example then that might explain why the little ones were placed for adoption.
It's just a theory.
Have you contacted any of the children of the older offspring of Phyllis, incase their parent told them how come the family ended up split, or indeed if they know anything about TFP?
Frederick J Penfold would have been a teenager when the break up was taking place, Vera would have been approaching 10.