Brian
What you have is the standard ICO "first response". In too many words, they are saying they are trying to seek an informal solution and have gently reminded MoD of their 20 day obligation.
I think you'll find MoD will respond to that prompt, but perhaps come up with an excuse not to supply any or all you ask. If this happens, go back to the ICO and they will make a judgment on whether the excuses are valid.
However, AI R is right - the ICO are largely toothless, their position weakened by the rather vague legislation. For example, MoD may be obliged to supply information, but the ICO has confirmed there is no legal requirement for it to be accurate or truthful.