There are numerous libraries within central government departments and regional government and their access policies can vary considerably. It is essential therefore that you contact the individual libraries concerned in advance of any planned visit because some of them may offer no public access at all.

These two books are good sources of contact information for Government and Special libraries in the UK, your home library may have copies for you to consult:

• Aslib Directory of information sources in the United Kingdom (London: Europa Publications, 2006)
• Guide to Libraries and Information Services in Government Departments and other Organisations. (London: British Library publishing, 2004)