The solution is simple. Continue calling the boat Boaty McBoatface. Ignore all references to the government's preferred name. They can choose what's painted on the side, but the name depends only on what people call it. If enough people call it Boaty McBoatface its name really is Boaty McBoatface. If your job depends on calling it the government's preferred name then subtly alter the timing of your speech to make it…
And regardless I doubt anyone will call it "Boaty McBoatface". It'll be abbreviated into something anyway. BMBM or Boaty or something.
And it will demonstrate that resistance is futile!