From my researches it would appear that the majority of English Coells lived either in Essex or the East End of London. Although the surname is fairly rare I am aware that over the years this has no doubt been corrupted e.g. Coel, Coal, Cole, Cowl, Cowel and Cowell.
My line includes:-
Thomas Coell - Labourer born late 1700s / early 1800s, his son Charles Coell - Gardener born early 1800s who married Sophia Slater (born 1803 High Street, Poplar) in September 1840 at St Mary Magdalene, Woolwich (then Kent). They had one son Thomas Edward Coell born April 1845 in Ford Street, Bow, and possibly a daughter. By 1871 Thomas is living with his mother, now a widow, in Devonshire Street, Mile End Old Town. Thomas worked as a dock clerk in the London Docks. In November 1883 he married Alice Mary Ann Deacon (born 1861 Alverstoke, Hampshire).
They had 4 children; Bertram Edward Coell born 1885, Leonard Thomas Coell born 1887, Grace Coell born and died 1895 and Dorothy Alice Coell born 1896 all in West Ham.
I can go forward from here but I really want to go backwards starting with Charles and his father Thomas. Hopefully someone out there has a connection.