Copac is a free service, available from anywhere at http://copac.ac.uk which brings together the catalogues of over 70 UK and Irish libraries. Using Copac you can discover the holdings of the UK's national libraries, many university and specialist research libraries. The range of libraries include the British Library, Oxford and Cambridge universities, the National Trust, major Russian and East European collections, Middle Temple and Mechanical Engineers library. The Catalogue of the National Archive is also a very recent addition.
Copac covers a vast number of subjects and specialisms and can help researchers quickly and easily discover and locate a huge amount of material. You can search across all libraries or limit to an individual library - select 'Main search' and scroll down to see various options to limit your search