In thirty odd years, I have never established who Charles' mother was. There are two marriages in the 1760s - which seem too early - and one in 1790, apparently too late: Thomas Pierce who marries Mary Ede, a blacksmith at Lindfield.
In 1851, a Philip Pierce b c 1803 is living at Picknowle, Cowfold, with his father Thomas aged 80, so born c 1771.
Extracts of manorial documents online make it clear that there were two Picknowles:
https://archive.org/stream/sussexarc...e/170/mode/2up
and that they were clearly being rented out to tenants.
Is this Thomas Charles' father? (family search notes some Cowfold burials, but doesn't give age at burial) His brother? A cousin?
I'm not sure this advances the search, but I present it in case anyone else has suggestions. I thought manorial records might be a way forward, but Charles' son (another Thomas) was clearly a tenant farmer on short leases or annual rental as he is forever moving.