Consider the types of materials you wish to locate and if available try and refine your search results using these otherwise you may wish to add appropriate search terms such as reports, technical reports, conference proceedings.
The following resources search for all types of grey literature but are particularly useful for finding conference proceedings and doctoral theses.
The following resources provide information produced by the UK government and its agencies. Information available includes governmental publications, policy documents, consultations and announcements.
A Think tank is a body of experts that performs research and provides advice and ideas in specific areas. Some examples are here: https://www.theguardian.com/politics/2013/sep/30/list-thinktanks-uk
Economics think tanks ( from LSE Library).
They cover topics relating to social, economic and political issues for example.
Information is available through their own reports, expert commentaries and analysis, blogs and videos.
Repositories are collections of research produced by an institution's researchers. Institutions can be governmental, organisational and academic, such as Universities. Often contain electronic PhD theses.
City Research Online, the repository of City, University of London has had a recent update to its interface and searching.
The following resources allow you to search institutional repositories which can contain grey literature.
The following resources allow you to search for doctorate theses and dissertations relating to your research topic