Ah, here they are in 1851:
https://www.ancestry.co.uk/imageview...turn&pId=77017
Harriett Mansfield Head Widow 26 Chairwoman Tenderden Kent
James Do Son 6 St Martins Middlesex
Elizabeth Do Daur 1 Do Do.
No wonder I never found them by looking for a family with a 1 year old daughter named Harriet.