First of all, the British accent of the mid- to late-1700s is not the same as the British accent of the present day. Accents, like languages, evolve over years, decades, and centuries. Second, there are several British accents, including Scottish, Welsh, and Irish. It is impossible to know for certain what accent George Washington used. read more
Likely, he had an American accent, but it would not have been as significantly different as someone's English in Britain, as it would be today. read more
Short answer: what Washington spoke would doubtless have sounded much like accents in particular parts of England in his day, because it had descended from them (in the previous century). The answer to your question depends on what you have in mind by a "British accent". read more
Discussing the accent he used for Washington in an interview with The Onion AV Club, he explained: The accent back then was probably nothing like what we think of as a Southern accent now or a New England accent now, so we tried to find the root of the accents. read more