Some UK French special collections of manuscripts can be located using the Archives Hub. One example of such a collection is the collection of letters from J.K. Huysmans to Arnold Goffin in the Liddle Collection of Leeds University.
Special collections of books can be more difficult to track down. Glasgow University has got the Ferguson collection (Sp Coll Ferguson Ag-d.) including some 16-18th century French books on magic and the supernatural.
Leeds University has a collection of early French books. This consists of works in French published between 1567 and 1899, the great majority falling between the dates 1650-1800. They were mainly purchased from special grants made to Paul Barbier, Professor of French at the University of Leeds 1903-1938, for his distinguished lexicographical work. The subjects are very wide-ranging and include travel and topography, French language and literature, European history, philosophy, politics, economics, education, natural history, horticulture and science. Most of the works in the collection are by French authors, but there are some translations, and also some foreign imprints.