Hi Deb,
Went back to the library today just to double check the baptisms from 1780-1783 for Mary Paradise and EUREKA!

here's your missing link!
Baptism: 6th July 1783 Mary daughter of John & Mary Paradise
For some reason this baptism was not recorded in the index which is why I think I missed it the last time I looked for it. (This time I looked through all of the baptisms individually.)
I also found this baptism for a John Paradice which would fit timewise with your John Paradise who married Mary Mayo in 1780
12th June 1752 John son of Thomas & Mary Paradice
A little more info on the John Totty Mayo line:
Marriage details for John Totty & Mary Mayo's son John (who was the other witness to the marriage of William Mayo and Mary Butson)
Date: 9th April 1839
Place: St Nicolas Church Newbury
Groom: John Mayo, of Full Age, Bachelor, Occ: Whitesmith of Newbury
Bride: Sarah Brown, of Full Age, Spinster, Occ: Servant of Newbury
Groom's Father:
John Totty Mayo Occ; SextonBride's Father: Robert Brown Occ: Labourer
Witnesses:
John Totty Mayo and Jane or Jone Mayo
Both Bride and Groom signed their names
This looks like them in 1841:
https://tinyurl.com/l7h38puand in 1851:
https://tinyurl.com/mtpo85uand his Baptism:
https://tinyurl.com/kxw8jyvwhich records his baptism in Thatcham (approx 4 miles east of Newbury)
so sometime between 1813 and 1816 the family must have moved from Wantage.
In the church records for St Nicolas Newbury there were the following baptisms for children of John & Mary Mayo (can't be sure but think that this is John Totty and Mary Mayo):
Baptism: 15/8/1804 Jane (born 12/6/1804) <<<<possibly Jane Mayo witness of above marriage
Baptism: 3/8/1806 Mary Anne (born 11/1/1806)
Baptism: 23/12/1807 Robert (born 1/10/1807)
Chris