Hi,
Welcome to Rootschat!

I'm afraid I don't know anything about your Stuart Family but did you know the main Cemetery between Grangemouth and Polmont is called Grandsable Cemetery?
As you enter the cemetery, there is a largish house just inside the gates. How old this building is, I don't know, but even if it doesn't date back far enough to the 'the' Grandsable House', it may well be a newer building on the same site? The Cemetery was established roughly towards the end of the 1880's so might have been part of Grandsable House's land?
On the 1881 Census, there is only one match:
Dwelling:
GrandsableCensus Place: Polmont, Stirlingshire
Head: John McKinlay, Occupation: Book-keeper *Colly??, age 69, born at Douglas, Lanarkshire
Wife: Mary Murray McKinlay, age 68, born Muirkirk, Aryshire
Son: Duncan Mc K. McKinlay, Occupation: Artist (Figure Painter), age 24, born Muirkirk, Ayrshire. (Unmarried)
Servant: Catherine SWAN, Occupation: General Servant, age 14, born Falkirk, Stirlingshire.
*Colly might be an abbreviation for Colliery?You could try contacting Falkirk Archives:
http://www.falkirk.gov.uk/services/community/cultural_services/museums/archives/archive.aspxGood Luck,
Anne