Kate,
William Heath & J. G. Bullingham, of 24 George Street, Plymouth. Heath was originally an optician, Bullingham joined the partnership as a photographer.
The W. H. Smith M.P. mentioned was William Henry Smith who was a great friend and advocate of Lord Chelmsford. He was Member of Parliament for Westminster. His father, also William Henry Smith, founded the newsagents and bookseller company and when the younger W. H. Smith left school the company became and remains W. H. Smith & Son.
JY