To locate material not held by UCL you can use the Library Hub Discover site: an online catalogue with records of the holdings the top research libraries in the country.
Senate House Library has strong collections in languages, the arts and social and historical sciences. Any registered member of UCL can join the library and borrow from there. You can pre-register online.
The Interlending and Document Supply service can be used to request items not held in any of the UCL Libraries. On the Interlending and Document Supply service webpage you can find more information on how to request materials.
Search - Library Hub Discover (Jisc)
Library Hub DiscoverLibrary Hub Discover, gives access to details of materials held in many UK national, academic and specialist libraries. It contains content created and contributed by 160 institutions.
British Library Main CatalogueThe British Library Main catalogue contains millions of records for books, journals, newspapers, printed maps, scores, electronic resources, sound archive items etc. held in the Library's collections