Hi Teresa & David
Thanks for your replies
The things I know for definite are:-
Great grandfather "William Avern" born in Coventry 1854
Great great grandfather "William Avern" married Maria Hayes in Leicester in 1846 aged 25 (1881 census says he was born in Coventry) Marriage certificate says his father was another "William Avern"
I am now just clutching at straws. I have found a "William Avern" who died in Coventry in 1871 aged 77 which would tie in with the "William Avern" who was christened in Rowington in 1795 son of James & Mary-Ann
I hope this all makes sense (why did they all have to be called "William"