I do have Ann Hancock d Wlm And Mary bap 24 Sep 1740 that would fit with the wedding in 1739 but then there's a big gap
Thomas bap 10 Dec 1749.I have five Hancock's born to William and Mary between 1749 1763: 49; 51; 55; 60; 63

There is a William Hancock s George and Jane b.19 Nov 1738 but I don't know if it's the right William. Other Ancestry Trees have his father as George so it seems it's the correct one.