Some responses:

I did use the postal service: it's cheaper and much more convenient. As I am not home during the day, I just have to pick my parcel up at the nearby drugstore.
Geoffrey Taylor does make man-made fibers kilt: what about polyviscose?
I wanted my kilt to be listed among serious garments, not other other ones in other other fibers...
To get my kilt as a gift would be a lie... Geoffrey is a serious company. If they gave all their kilts, I think the British Revenue would inquiry...

As a matter of fact, my hoses were listed among cotton knitted goods... But they had to guess, and it's the same rate...

Interestingn fact: if I got a kilt from the US, I would have to pay taxes, but no custom fees: NAFTA. If I got a kilt from my province, I would have to pay taxes (federal and provincial). If I got a kilt from another province, the vendor would charge me the federal tax, but I would have to send the provincial tax from my own initiative to the Ministre du Revenu du Québec... I wonder if anyone does that...