Hi Robbie,
Here's what I've managed to "dig-up" for you, no William Boyd though, sorry. (Or his 2nd wife)
There is a monumental inscription in the old churchyard that reads -
"1854 This is the intended burial place of James Hepburn and Margaret Douglas. Their daughter Margaret died 3rd March 1893 aged 76 years. Her husband Thomas Smith died 23rd August 1876 aged 65 years".
The burial records for the old churchyard plots only begin in the last quarter of the 19th century, so there will, no doubt, have been many internments between 1854 (the date of the erection of the headstone) and Thomas' death in 1876. For this plot the entries are as follows -
(All subsquent dates are of internment)
Owners of this plot were James Hepburn and Margaret Douglas.
Interred in the South lair -
MARGARET SMITH, aged 63 years, 4th September 1896.
Interred in the Centre lair -
MARGARET SMITH, aged 76 years, 6th March 1893.
Interred in the North lair -
JOHN SMITH, aged 7 years, 6th December 1892.
JOHN SMITH, aged 10 months, 24th January 1893.
-------------------------
The next 2 are "Pauper burials".
THOMAS CHALMERS, Newmains, aged 7 weeks.
Parents - Robert Chalmers and Margaret Boyd.
Interred in common ground. 7th January 1867.
JANE BOYD, housewife, Newmains, aged 54 years, married.
Parents - James Hepburn and Margaret Douglas.
Interred in the old churchyard, 30th March 1868.
(She may well have been put in the Hepburn family plot).
The following 11 burials are all in one plot in the old walled "Private" burial ground, adjacent to the old churchyard. The plot number is 604.
MARY JANE CHALMERS, housewife, Newmains, aged 55 years, married.
Parents - William Dunbar and Jane Miller.
Interred 1st May 1877.
THOMAS CHALMERS, furnace keeper, Newmains, aged 59 years, widower.
Parents - Thomas Chalmers and Elizabeth Stevenson.
Interred 22nd March 1880.
WILLIAM CHALMERS, Mossneuk, aged 6 years.
Parents - Robert Chalmers and Margaret Boyd.
Interred 1st September 1881.
MARGARET CHALMERS, housewife, Newmains, aged 40 years, married.
Parents - William Boyd and Jane Hepburn.
Interred 2nd March 1885.
ROBERT CHALMERS, coal miner, Newmains, aged 40 years, widower.
Parents - Thomas Chalmers and Mary Jane Dunbar.
Interred 7th June 1886.
JOHN CHALMERS, Newmains, aged 5 years.
Parents - Robert Chalmers and Margaret Boyd.
Interred 6th June 1887.
MARY JANE D. CHALMERS, Newmains, aged 9 months.
Parents - William Chalmers and Fanny Weir.
Interred 19th January 1895.
SAMUEL CHALMERS, Cambusnethan, aged 1 month.
Parents - Samuel Chalmers and Isabella Paterson.
Interred 9th April 1896.
SAMUEL CHALMERS, miner, Cambusnethan, aged 23 years, married.
Parents - Robert Chalmers and Margaret Boyd.
Interred 1st July 1896.
MAGGIE CHALMERS, Newmains, aged 1 year 8 months.
Parents - James Chalmers and Marion McEwan.
Interred 16th September 1898.
NEWBORN MALE CHALMERS, Crindledyke, aged "few minutes".
Parents - Thomas Chalmers and Margaret Stewart.
Interred 28th September 1898.
The next (and last) 2 are buried in the new cemetery.
MARGARET MOONEY CHALMERS, schoolgirl, Newmains, aged 12 years 11 months.
Parents - William Chalmers and Fanny Weir.
Interred section E1845. 9th March 1910.
Plot owner - William Chalmers, coal miner, 20 Main Street Newmains.
JOHN CHALMERS, coal miner, died Glasgow royal Infirmary, usual residence Newmains. Aged 53 years, married.
Parents - Thomas Chalmers and Mary Jane Dunbar.
Interred section E1629. 15th April 1912.
Plot owner - Thomas Chalmers, coal miner, 22 Houldsworth Street Newmains.
(There are some internments for the children of John Boyd and Abigail Borland, also children of George Boyd and Martha Morton. Ring any bells?)
Hope this helps,
Lodger.