Hi Maureen ...
The 10 HAN(D)COCK baptism at Charlbury are as follows:
1749 - Thomas
1750 - William
1755 - Thomas
1760 - Mary
1763 - Vestye
1777 - Thomas
1780 - William
1783 - Charlotte
1785 - Richard
1788 - Mary
There are two possible marriages:
27 OCT 1739 - William HANCOCK to Mary MIDWINTER (both of Finstock) at Charlbury
02 OCT 1744 - William HANCOCK to Mary SOMERSBY (both of Finstock) at Charlbury
It's possible that either of these couples could be the parents of the first five listed above, as they could be having children for 20/25 years.
As there's a 14 year gap between Vestye and the next baptism, it's likely that she was the youngest of this particular family.
There's no indication on the marriage index that the second William was a widower (it is often recorded), but I suppose it's always possible that they are both the same person.
If either of these Williams is the father of Vestye, then he cannot be the William (s. George) that you have baptised in 1738 (this is why it's always dangerous to "leapfrog" a generation!).
Note: There are no separate registers for Finstock at this time - all BMDs are recorded at Charlbury.
Penny