Thank you Yokel, that is strange, as I checked the IGI site the other day, but immediately found them after your post.
This does answer the immediate issue about the marriages, and confirms ONE William and Susan, their Banns record is available on the PR under Wretton images 21 and 22, and both tie up with the marriage.
My understanding is that Wretton was used by the Stoke Ferry parish for a period of time, so perhaps the two bapts are for that reason, if the couple specifically wanted her bapt in their church.
The entries are signed by the same clerk, and other couples don't appear to have 2 bapts.
Just found the full details of the children of William and Sarah in Stoke Ferry
Sarah Ann bapt 10-1-1847 buried 14-3-1847 age 14w
Sarah ann bapt 2-1-1848
David William bapt 3-3-1849
George bapt 2-2-1851 buried 20-8-1852 aged 1
George bapt 17-10-1852 buried 8-3-1860 aged 7 diphtheria
John bapt 26-2-1854 buried 19-4-1860 aged 6
Emma bapt 20-1-1856 buried 22-3-1860 aged 4
Susan bapt 22-8-1858 buried 15-4-1860 aged 1
Arthur bapt 1-1-1860
Emma bapt 4-5-1862
George bapt 4-9-1864
John bapt 6-5-1866
Susan Lydia bapt 17-1-1868
This certainly ties up with the birth and death records for Downham Reg Dist, I accept there are 40 parishes in this District.