There are Sam pieces at various museums and private collections.

V&A

Bristol 

Plymouth Art Centre

Rochdale Art Gallery

Southampton City Art Gallery

http://www.bbc.co.uk/arts/yourpaintings/paintings/bathers-in-southampton-water-18257

Bathers in Southampton Water

The Yale University Library, USA has a collection

http://www.library.yale.edu/ or

http://drs.library.yale.edu:8083/HLTransformer/HLTransServlet?stylename=yul.ead2002.xhtml.xsl&pid=ycba:mss.0014&query=sam%20smith&clear-stylesheet-cache=yes&hlon=yes&filter=&hitPageStart=1#