Real funny. Agree with those above, it would be nice to read the PM's response to the letter. But also the reaction of Professor McGonnagal and Headmaster Dumbledore.
Author's response
I did actually think about that, but then I realized that the Prime Minister's response would not be funny. It would, in fact, be dead serious; a grown-up politician would not start slinging the same kind of insults, and given the Prime Minister's reaction to wizards in canon, he would take this very seriously.
So including his answer and following events in any detail would have pretty much killed the comedy of the entire story.
Therefore -- sorry, but no response from the Prime Minister, or reactions from the Hogwarts staff.