So you pay postage from your parcel in country X, and on arrival in the UK, it's held, sometime for customs and/or VAT -- and then the carrier tries to charge you up to £20 for 'handling fee' to deliver it to you.
Basically what they do is try to hold you hostage to pay for the delivery, even tho you have paid postage already AND they are supposed to have an agreement with the oversea mailers about it.
It's really daylight robbery. And they all do it. Royal Mail, DHL, Fedex etc.