bugger it up, basically.

Anything over £15 coming from outside the EU incurs an import duty. Recent and IMNSHO a rouse to pay for Brexshit.
On April 1st (who decided that?) or whenever, a No Deal Brexshit will incur the same penalty. The answer (I learned from experience) is when buying more than one low value item (post free) - buy several times individually, though if on Amazon - watch the price go up.

One pair of silly shoes listed at £24 from wish.com (which has a UK address), but the item came direct from China with a declared value of $6. That's the wheeze they can play and increasingly I see it on EBay.
I got most of the value the first day I wore them, and the festival season is upon us!