Hi have found several Benjamins on the 1841 census so I had a look for a birth/chr date to help narrow it down and found 2 for around the birth year you gave.
Benjamin Finney chr 15 Jul 1827 Alton parents Benjamin and Ann
Benjamin Finney chr 4 May 1828 Ellastone parents William and Maria.
This was from the Finney uk page on Rootsweb you should check it out
http://freepages.genealogy.rootsweb.com/~finney/igi/finney-igi-b.htmHere are the Benjamins I found on the census
Benjamin Finney 55 Farmer
Ann Finney 50
Benjamin " 14
Anne " 7
Hannah " 5
Living the Dale, Wootton, Staffordshire
William Finney 40 Shoe maker
Maria Finney 37
John Finney 10
Thomas " 7
William " 5
Samuel " 1
Charles " 21 Shop........
William Deakin 20 Shoe maker apprentice
Living in Wootton.
I am more inclined to think he is the son of Ben and Anne??
There were no other Benjamins of this age the rest were 25,25, and 30.
Can't find Fanny for you though I tried Ipstone and there are quite a few Critchlows but no Fanny's. I don't have the Derbyshire census so she could be in Sturston.
I did check around Ellastone in case that she might have been there but the only Critchlows I could find was a Thomas Critchlow age 70 with his wife age 75. Thomas was a farmer and not from Staffordshire so could be grandparents of Fanny moved from Derbyshire to Upper Cotton (This is where they are on the census) and could be a connection to how Fanny and Benjamin met?

This is just fanciful thinking don't take it too seriously.
Hope this helps some bit. All the best Anjo