Hello Insom,
After finding no sign of a Laura Isabell Bagnall, I took a look at the marriage on FreeBMD it gave two possible marriages the 2nd one was that Laura could have married Septimus Bell - and I think she just may have.
Found this 1901 Sunderland Durham re:RG13 4712/181/61
25 Ann Street
Septimus Bell age 29 Foreman Wharf b, Durham
Laura I Bell age 25 b. "
Albert V Bell age 10 months b. "
Had a quick look back on the 1891 and 1881 census it would appear that Septimus and Mark Bell were brothers.
I think it would certainly be worth a look in to.
Hope this helps
Regards
Pauline