This Public Account Committee report contains shocking figures for MOD empties - currently running at 17% of the stock. Most appear to be lettable based on the analysis of condition categories. Hundreds of properties have been empty for an average of 5 months solely because the MOD doesn't have a simple way of getting carpets into them!
The report also contains some interesting insight into how Council Tax works in MOD properties. It is not clear whether the money raised goes back to the government as with most Council Tax or is retained locally.