Importing second-hand machine spares into the UK

I am thinking of buying some used machine parts from the US. I've not done this before, although I have bought horological stuff from several non-EU countries. VAT and Customs duty will be payable to the Post Office, not HMRC directly. I have had a poor experience with a US-sourced shipment when I paid duty on a $100 (USD) item as if it were £100, and paid VAT on a non-VAT item.

To avoid misunderstandings over customs duty and subsequent VAT what is the best description the seller can provide? I'm not looking for a loop-hole, just a way to avoid problems.

For an idea of value the item is approximately £200 and shipping is nearly £70 - it's bulky.

I would appreciate any advice you may have.

Regards
D

If it is through eBay, they now have an international shipping program that covers all charges, so you know in advance what it's going to cost you.

I've used this system and it works well, I've also brought stuff in a few times before this arrangement started, and not only do you not know a final price until you get it, the timescale varies enormously. The new system sails through customs, whereas before it could be in their hands for weeks!

For one shipment (a whole load of powered tooling for my Traub 5 axis lathe) the seller put it in six 'fixed rate boxes' that the US Post Office offer. Five came whizzing through within a week door to door, the sixth took over a month !

This lot weighed a fair few pounds and cost even more !!!