I realised the same fact when I decided I wanted a zendrum, so I contacted the very helpful people that make them to see if they had an experience. They put me through to some people in the UK who have bought zendrums in the past and the result was that there isn't really a way around VAT, unless you're in some way dissabled. And if you really want to get around the potential duties/tarrifs you can try to get a specific product code from the HMR labling it as a unique product that can't be bought in the UK, meaning theres no market in the UK or even EU to protect by enforcing the tarrifs. owever i'd expect that process to be very beurocratic, long and potentialy costly anyway, when the duties, mentioned by someone I was put in contact with, are only around 3-4%
Also, I have a friend who works in a music store, he builds custom guitars for people and I was quite shocked to hear that the minimum for a standard custom was around £1300, expensive woods crank that up even more. So comparatively, even after tax you're gonna be getting a custom insturment for less than a guitarist could.