The only undertaker at this address I came across is Edwin Howard Terry. Prior to becoming an undertaker, E. H. Terry was working as a carpenter at Sussex Place (nowadays Ferdinand Place), Camden. However he went bankrupt in 1865. He later moved to 232 Great College Street (nowadays Royal College Street), where he opened a funeral parlour. For several years everything went well but by the late 1870s his financial situation deteriorated. In 1879 proceedings for the liquidation of his company began. They were completed in 1880 but E. H. Terry may have continued to work as an undertaker for a few more months. He was still listed as such in the 1882 edition of the Post Office London Directory. After that his name no longer appears in any trade directory.
E. H. Terry himself does not really account for the plural "Undertakers" (it does not look as if there could be an apostrophe before the "S"). Yet after him the premises were occupied by the Royal London Friendly Society and later by a bootmaker. I could not find any undertaker who could have been there before either.
Location: Wilmot Place / Pictures taken in November 2012 and July 2013