Well perhaps Charles was very unlucky and married another wife before the mum of Thomas and Edward. And she died. Evans definitely gives his father on his marriage certificate as Charles a tailor, and Charles (his brother according to the census for 1841 says he was born in the Isle of Man whereas Evans says Lancashire. But as Catherine and Charles (the son) were the same age on the census I thought Thomas was their son and Evans was uncle to Thomas.
I have never found the birth entry for Evans, and I have been looking since 1984! Like you I thought you had found mum for me. Never mind. Back to the drawing board.
Thanks again - I don't suppose the death of Elizabeth Callister could be wrongly transcribed, so she died not in 1821 but 1827. That would work!
Clutching at straws.

and thanks again