I think you will find that the Nine Tailors saying predated the Sayers reference and the Fen tradition. I believe it was used by Elizabeth the first who is reported to have begun her reply to a petition by eighteen tailors with the words: “Gentlemen both.”
The saying has also been documented in France and Germany. The same phrase appeared in William Hicke's 'Grammatical Drollery' in 1682.
Hicke was not wildly keen on the phrase and came up with the story of a group of tailors rescuing one of their own from destitution.

“There is a proverb which has been of old,
And many men have likewise been so bold,
To the discredit of the Taylor’s Trade,
Nine Taylors go to make up a man, they said.
But for their credit I’ll unriddle it t’ye:
A draper once fell into povertie,
Nine Tayors joyn’d their purses together then,
To set him up, and make him a man again.”

The belittlement of the blameless tailor was compounded by the story that an evil servant having witnessed nine tailors working for her mistress and getting paid more than she, battered them with a black pudding! The tailors were so terrified by the black pudding, they handed over all the money. As a vegetarian I have some sympathy! I'm not sure with whom though.