FWIW, the same can be said of pretty much any shipment coming TO the UK (and I assume Europe)
I have always advised any shipper - and my in laws are in Texas - to use USPS as FedEx/DHL/UPS always sting us for anything they can handling/duty wise. Indeed, I left a pair of shoes there once and father-in-law shipped them to me UPS and I paid duty on my own shoes.
That said, Dan Caron sent me a new fuel gauge by regular (Canadian) post that took ages to come. I was in no hurry for it, but it took so long I had to ask if he had indeed sent it. Sometimes the post is quick, other times....
And then the Mail this end. They are losing cash, and soon to be sold/privatised (ggrr). As such, some bloody accountant (sorry Cees) has put them on to the fact that they too can raise revenue by investigating / charging/pre-paying duty. I have had a couple of things of late (including the fuel gauge) that I was charged on at this end. It looks like that little loophole is being closed
But yes, the 19% TVU (or 15% VAT in the UK) should NOT be charged if the goods are leaving the EU. Just so you know, I really object to paying state sales tax for similar reasons (albeit the % is lower)