Say what you like about estate agents, they are sometimes extremely helpful when trying to identify people of property from the past. Courtenays have published some of the history of the Clapham Abbeville Road and environs and include this: "The Clock House estate was the next to be developed. .... John Kemp-Welch, proprietor of Jacob Schweppe & Co, who bought the house in 1862 sold it for development in 1885." That is surely our man. And it was probably his executors who sold the estate, not him.
Difford's Guide gives: "The 1st June 1834 marks another turning point in the history of Schweppes, as this is when two new owners took over the business, John Kemp-Welch, a wine merchant and William Evill, a prosperous silversmith, both from Bath."
And the Peerage provides Kemp-Welch's dates and: born Dorset, died Christchurch, Hampshire.
Sadly we could find no image of Kemp-Welch so an early Schweppes bottle is standing in for him.