They are indeed a close match, and I was inclined to believe it until I saw the 1851 census which listed William and Eliza Evans at Quarryduon, and lists the births of the children at Spittal:
1851:
William Evans 48
Eliza Evans 45
Morris Evans 12, Spittal
Anne Evans 10, Spittal
James Evans 8, Spittal
John Evans 6, Ambleston
Sarah Evans 2, Ambleston
Mary is already living away from home by then.
From this I began looking for them in Spittal 1841 and got:
William Evans 38
Eliza Evans 35
Arnold Evans 10
Mary Evans 8
Martha Evans 6
Morris Evans 4
Anne Evans 3/4 of a year old
But thank you for your help, as you did indeed point me in the right direction!