Many thanks for the reply. I came across a diary called 'No Continuing City' which is a diary and letters of John Burgess of Ditchling, Sussex 1765-1819. He is a baptist and his brother in law is Edward Billinghurst married to Sarah Edwards of Plumpton. John Burgess's wife is the sister to Sarah. It is a fascinating look at his life and the distances they all travelled to attend the Baptist meetings.
I have Farncombe's mothers name as Sarah from the BMD so I had put two and two together and thought that the Edward and Sarah mentioned in the diary were Henry, Farncomb and John's parents. I cannot find a marriage of an Edward to an Anne. The diary also mentions a Thomas Billinghurst at East Grinsted and another Mr Billinghurst in Chailey.
This really does promt me to make a visit to the Sussex records office.