I have tried to speak to UPS, but I just got fed up with being connected to an endless number of people where none could even remotely explain the basis for this charge. I simply don't have the time or the energy to fight this, so I bit the bullet and paid up. Depending on how Meermin will handle this, I'll decide on whether I will consider making future orders or not.
Look a few pages back in this thread, and you'll see that meermin used the wrong customs code. Doesn't seem to hard to rectify if you know both the codes. Or you could just contact that poster and ask him how he solved it.