Hi Sherlock,
Here's a wee bit more info on the children irret kindly found for you - just in case you ever want anything further
(From the British Vital Records)
CHAPMAN, James
Gender: Male
Birth Date: 23 Apr 1748
Christening Date: 29 Apr 1748
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Gavin CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
CHAPMAN, William
Gender: Male
Birth Date: 29 Jan 1753
Birthplace: Bothwell, Lanark, Scotland
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Gavin CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
CHAPMAN, Elizabeth
Gender: Female
Birth Date: Feb 1755
Birthplace: Bothwell, Lanark, Scotland
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Gavin CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
CHAPMAN, Margrat
Gender: Female
Birth Date: 26 Jul 1757
Birthplace: Bothwell, Lanark, Scotland
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Gavin CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
CHAPMAN, Mary
Gender: Female
Birth Date: 12 Aug 1760
Christening Date: 17 Aug 1760
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Gavin CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
Could this be Gavin?
CHAPMAN, Gavine
Gender: Male
Birth Date: 12 Dec 1721
Christening Date: 15 Dec 1721
Recorded in: Bothwell, Lanarkshire, Scotland
Father: Matthew CHAPMAN
Mother: Janet FORREST
Source: FHL Film 1042964 Dates: 1709 - 1820
There were 8 Janet Forrests born in Lanarkshire between 1722 and 1733 but none of them born in Bothwell itself.
The best you can hope to get is a 'Proclamation of Banns' for Gavin and Janet's marriage as it's way before statutory regsitration. The BVRs don't have anything.
If you'd like any details of the Janet's I mentioned above, just let me know.
Anne