Looks like there were six in 1843. See cover of sheet music at Wikipedia. Apparently they also used the name Boston Minstrels.

The Illustrated London News. 1843-1844, contained a picture of the Ethiopian Serenaders, "five minstrel players..." A statement in the book "Tap Roots" by Mark Knowles.
Pelham is mentioned in an 1846 English pamphlet as a bones and tambourine player (book, Inside the Minstrel Mask, Bean et al.). Henry Mayhew, in London Labour and the London Poor, mentions Pell as as example taken by a street performer.

The early E. S. included Tony Winnemore and -. Quinn. In "Burnt Cork and Tambourines" a J. Dumbolton is mentioned as their agent (the five mentioned previously) when they went to England in 1846, (Palmo Opera House and St. James, and Arundel for the Queen).
www.circushistory.org/Cork/BurntCork5.htm

Sorry, nothing about four originals going to England in 1843.