Marriage request 1870-1890 Lucas

[Mary-Anne]

Searching for marriage between Henry James Lucas and Constance Ethel Jones (my great grandparents) probably in London or surrounding districts.  My g'mother Amelia Elizabeth was born in 1890-91, so am assuming they married during the decade before.

Have checked the registry index but can't see a marriage with these two names.

A Rootschat helper found a Constance and Henry Lucas in Islington in 1891 census but children don't all seem right  (+no grandma) and also can't find them in the 1901 census. (the Amelia I found in 1901 census had different parents).

Am I looking in the wrong district?
Is there somewhere else to look up marriages?
Can someone help please?
Mary-Anne