They were in Whitehaven- the surname was fine

1861
96 Mount Pleasant
Mathew MILLS 50 Nailor (Journeyman), Carlisle
Jane 52 Gen Dealer, Lancs Wigan
The census registrar has added "Mason" to Matt's occupation. I believe he must have read the occupation as "Waller" to have reached that conclusion, but it's clearly Nailor

I see he was a Nail Maker in 1851 and living at Mount Pleasant.