You should take a look at that IMAGE, as there is a slight chance that it has more information, particularly tWilliam's Occupation.
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Assuming that this is the correct family, there are no signs of any involvement with Manchester; and as that 1841 UK Census was "United Kingdom Census 1841 - Sunday, 6 June", it leaves very little time before his Death, to move to England and make an impression great enough to warrant a statue - unless it was something significantly heroic etc.
The family Birth Locations do not show either a Manchester nor and England connection, so again making it unlikely that the family lived there for any significant period.
Today there is a "Lancefield Quay" in Glasgow, from which the last "ocean-going" Paddle Steamer operates "Doon the Watter".
I have come across an auctioneer's records including the sale of machinery from a Lancefield Foundry back in the 1960s.
I suggest that you contact the main Glasgow Libray, "The Mitchell" as it has the largest Reference Department in Europe, so may be able to assist you-
Glasgow Libraries The Mitchell North Street Glasgow G3 7DN Phone: 0141 287 2910 Fax: 0141 287 2815 Email: email@example.com
there is a "SANDYFORD Hotel" in Glasgow; but not directly on the Dumbarton Road; but being Sandyford Place, a section of the western part of Sauchiehall Street, may give some idea of location.
Lancefield Quay is about 1,000 yards (900 Metres) almost directly south of Sandyford Place, so not an excessive walk if these are the correct locations.
I have checked the 1842 Deaths again for England - none resemble William Naesmith.
Also the Scottish Deaths from 1841 to 1854, with none looking probable.
If William was also a Baptist, then The Mitchell may be able to ssist you find their local records.
Regarding the monument, I suspect that it is ,ore likely to have been a commemorative plaque; and given his age and location, I also suspect that it may have been in the Baptist Meeting House.