About Sir Walter. I certainly wouldn't put it past him to contrive a 'posh' pronunciation of Kellynch just to distinguish himself from the lower orders! It is also true that place names alter through time.

As an aside, it is fascinating to me how pronunciation of proper nouns varies over quite short distances. My family name was Leyman, which originates from Devon where it is pronounced Lee-man. Sixty miles to the east, in Dorset where I grew up, it is invariably pronounced Lay-man.