Hi Tramore,
The 1848 Marriage is on Familysearch with John as age 30. But FreeREG has transcribed him as age 20 which fits with his age on Census.
As I dont have access to a image of the actual Marriage I cant look at it.
So we need a Baptism for John with a Father THOMAS as per M/C.
I am sure this is him in 1841 in Wolverhampton, not with Parents though;
John Turner, 25, Miner
John ASTON, 15, Puddler, born in County*****
Sophia Johnson, 10, Sevant
Harriet Wild, 5