Empress Miniatures are having a small problem with their online store software.
From their website:
We are currently having problems with the shop software. Some sales are going through without the postage added to the price.
If your purchase is completed without the postage added, you will receive an email asking you to pay the missing postal charge. We will dispatch your order once this has been paid.
We are very sorry for this inconvenience but this has been caused by an upgrade which has gone wrong. Hopefully, Mr Site will sort it out soon.