I have no idea where John Drinkwater is buried.The book makes no mention of ancestors in Piddington.His ancestors originated from Tackley in Oxfordshire, and then moved on to Banbury.He was born in Leytonstone but travelled to many places round the country writing plays and poetry.
His grandfather was George Drinkwater but he married Eliza Sanderson.His great-grandfather was John Drinkwater who married Ann Wise. His great great grandfather Richard married Mary Holland, and his great great great grandfather Richard married Ann Pembery.
I can not find any Drinkwaters that tie in with those you mentioned however Tackley and Piddington are very close to eachother and the names George, Sarah and Elizabeth are very common in John Drinkwater's ancestors.
The Drinkwater's are very widely spread around that part of the country.There are 100s in Worcestershire, Gloucestershire and Oxfordshire.In his autobiography John Drinkwater talked about the amount of research he had done into his family tree and it is all pretty conclusive.
I obtained my copy of the autobiography from a secondhand dealer in the USA.It is in 2 parts and both are out of print.