I have searched Bevis Marks records but can find no marriage between Solomon/Saloman da Costa and Leah (?), so it is possible that they were married in another synagogue, not Sephardi.  It is also possible that in  spite of her Jewish name of Leah, she was not Jewish and they were married in a church.
I will try in the next day or so to search through the BM records for the forename Leah and see if I can trace her that way.
Regards
Martyn Woolf