Thank you, yes I did have those. Clement remarried, but maybe Sarah didn't get on with her stepmother or maybe she went to live with the uncle and aunt as soon as Clement was widowed and then stayed on with them.
I have now found a burial for Sarah Humphrey in 1825 (birth year calc as 1791) and several children including a Mary of the correct age bapt by Robert and Sarah Humphrey in Bury. So it looks like I have the direct connection between Sarah and the person who deposited the diary at the record office.
The thing I would really like to know is who were the uncle and aunt. Clement had a brother and sister that I definitely know of. My 3 x great grandfather was the brother. She refers to an uncle William which could be him. William doesn't marry until 1807, so couldn't be the uncle she is living with. Clement's sister (also called Sarah) married John Coot in 1796, so that's a possibility.
The other possibilities are siblings of her mother (Sarah Young). She mentions deaths of Aunt Parlett and Aunt Lee, I think Aunt Parlett is Susanna Parlett wife of James Parlett and Aunt Lee is Jane Lee wife of William, although if it is she is a few days out on date of death or the burial transcript is a few days wrong. If Susanna Parlett was same age as her husband approx, she could actually be a great aunt rather than an aunt.
Clement married Sarah Reed in Lyminster in 1796 - that caused me confusion too until I discovered he married two Sarahs.
added
big breakthrough!
found marriage of James Parlett and Susannah. She was Susannah Hammond they married in Bury on 9 Nov 1776. Now to connect her to Ann Hammond ( my 4 x great grandmother and Clement's mother)