Ashazoe - it's the location of the Fleet Air Arm Museum and all the archives relating to RN NCOs up to 1925 are now kept there. If you want anything later, you have to go to the Ministry of Defence and they will only release them to a spouse or parent for free (difficult if you're researching your grandfather or above!) otherwise it costs £30. I think the fee for the FAAM is about £25, but they give you the whole caboodle, including the list of every ship your relative served on and when.
When I contacted them they were very helpful and actually went out of their way to give me something that wasn't strictly speaking within their criteria. The member of staff there looked up all the Navy Lists up to my grandfather's retirement in 1945 to see his promotion dates and included that information too. I thought that was really nice of them.