Did a bit of poking around, it looks like there's a substantial collection of his materials at the Senate House Library at the University of London. [1] These

Did a bit of poking around, it looks like there's a substantial collection of his materials at the Senate House Library at the University of London. [1] These materials include quite a few interesting research angles: draft manuscripts of published works, unpublished stories, other ephemera including letters, & biographies by other authors. [1] http://www.ulrls.lon.ac.uk/resources/Pratchett.pdf http://www.ulrls.lon.ac.uk/resources/Pratchett.pdf