Found these snippets by Googling
WITHERBY, George Henry, stationer, Birchin Lane 1789L-1814P. Livery Sta. Co. by 1792. See Thomas Witherby.
WITHERBY, George, stationer, Nicholas Lane 1792U.
WITHERBY, Thomas, stationer, Birchin Lane 1759K-1765K; 9, Birchin Lane 1767K-1830P. Trading: as Thomas Witherby 1759K-1778K; as Thomas Witherby and son 1779K-1788K; as Thomas Witherby and sons 1789L-1800P; as William and George Henry Witherby 1801P-1814P; as W. G. and W. H. Witherby 1815P-1830P+. Free Coopers' Co. by 1767, livery by 1792. Sometimes described as law stationers. Common councillor Langbourne ward 1767-97. Firm established 1740, still existed as Witherby and Co. Ltd. 147, Cannon Street 1975. Son Thomas livery Coopers' Co. by 1792.
Found it here
http://www.devon.gov.uk/etched?_IXP_=1&_IXR=100165but I'm not sure what it's all about
