Heritage Open Days, 6th to 9th September. All free, most places not normally open the public. Something for everyone. Hopefully this link will take you to all the sites of Military interest currently listed around the UK. I recommend using the advanced search option as well. Other sites could well be added in the near future.
http://www.heritageopendays.org.uk/...wZXJ0eV9ldmVudF90eXBlIjtzOjg6Ik1pbGl0YXJ5Ijt9
http://www.heritageopendays.org.uk/...wZXJ0eV9ldmVudF90eXBlIjtzOjg6Ik1pbGl0YXJ5Ijt9