I am surprised that a DD size is causing you so much hassle, as someone in a similar boat (cup?!) but with a smaller number.
Slightly confused - I thought that the number is your back size and the letter is the cup, so does this not mean that they won't actually be able to reduce the 40 bit down? So you will end up for example as a 40B?

Or is it more an uplift than a reduction? Curious about how this kind of breast surgery works!
I absolutely agree with those saying it is your body, and no-one has the right to try to tell you what to do.