On a couple of occasions PM have issued us with considerable extra charges after a parcel has already been paid for and sent. They claim it is because of weight discrepancies. Yet we send the same parcel with them using the same courier many times and the weights are always the same and accurate (in fact we always add a couple of 100 grams to be sure).
We will not use PM again because at best they're incompetent and at worst fraudulent.