Having just been through the pre-1812 parish records for Newdigate I have found the records set out below. I haven't been able to link them to my wife's GADD family but I leave this for future Gad/Gadd researchers!
Happy New Year!
Bill
Baptisms
04-Jan 1739 Elizabeth, dau of Henry & Jane Gad
20-Mar 1741 Henry, son of Henry & Jane Gad
25-Dec 1768 Mary, dau of William Gad
19-Jan 1774 Charlotte, dau of William Gad
04-Mar 1792 Maria, dau of Charles & Mary Gad
19-Oct 1794 Elizabeth, dau of Charles & Mary Gad
14-Feb 1796 Allen? Anscome, son of James & Sarah Gad
11-Jun 1797 Harriet, dau of Charles & Mary Gad
24-Dec 1797 Richard, son of James & Sarah Gadd
05-May 1799 Charles, son of Charles & Mary Gad
26-Jan 1800 Jeremiah, son of James & Sarah Gad
15-Jul 1802 Sarah, dau of Charles & Mary Gad
02-Jan 1803 William, son of James & Sarah Gad
23-Jun 1805 John, son of James & Sarah Gad
20-Apr 1806 Thomas, son of Charles & Mary Gad
11-Feb 1810 Thomas Anscome, son of James & Sara Gad
Banns
18-Dec 1791 William Boxhall of Newdigate, widower to Hannah Gad of Newdigate, widow (other dates 25th Dec & 1st Jan 1792)
Marriages
02-Jan 1792 William Boxhall of Newdigate, widower to Hannah Gad of Newdigate, widow by banns, witnesses Stephen Burberry, Richd. Butcher
28-Jan 1790 John Boxhall of Tillington?, Sussex, bachelor to Charlotte Gad of Newdigate, spinster by licence, witnesses James Taylor, John Humphrey
Burials
30-Oct 1649 Widdow Gadde
14-May 1755 Mary Gad, dau of William
08-Jul 1765 Mary Gad, wife of William
28-Dec 1768 Mary Gad, infant
03-May 1774 William Gad, pauper
07-Nov 1788 Elenor Gad, dau of James, aged 1
22-Oct 1797 Harriet Gadde, dau of Charles & Mary, infant