The SOAS Library (School of Oriental and African Studies) has excellent collections for African, Asian and Middle East materials. It is available for reference use by an member of UCL, but only academic staff and research postgraduates may borrow.
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.
The Interlending & Document Supply service can be used to request items not held in any of the UCL Libraries. On the Interlending & Document Supply service webpage you can find more information on how to request materials.