As Sarah(1830) was in Newcastle in 1851, just a few years before Sarah(1854) was born, it might be worth checking the PR’s there, even though the 1861 census says that Sarah(1854) was born in Gateshead.
FreeBMD has some Sarah Hall births around that time, there is also a marriage ref Newcastle T 10b 114 Sept Q 1859 which only has three names
Sarah Hall
Ann Sewell
James Smart
If Sarah married James Smart

but if Ann married him who did Sarah marry

I have a couple who were baptising children which also had her maiden name on the birth cert, but could never find their marriage nor what happened to his first wife. Just discovered she had been living in the lunatic asylum for 30 years

Sorry I didn’t answer your post about the Norfolk Marriage Index, this is a CD sold by the Norfolk Family History Society and list marriages in Norfolk (obviously) from 1801 to 1837.
See
http://www.norfolkfhs.org.uk/bookstall/As you have the baptism for Sarah 1830, it might be worth posting a request on the Northumberland board for a lookup re Sarah 1854, put a link to this thread so people don't duplicate all lizdb's hard work
yokel