Has anybody bought anything from an EU country this year?

Carriers are charging differing fees for importing and I'm not sure what company to use to bring in a 700euro item. I can find the duty of 6% from here: https://www.trade-tariff.service.gov.uk/chapters/87

So the cost would appear to be: Item cost (converted to £) + 20%VAT + 6% duty + {carrier admin fee} + {other carrier fees} It is the latter two I am concerned about.

If I look at DHL, FedEx and UPS, it is almost impossible to determine how they are charging for this. It seems as if they may pay all charges on your behalf and then expect a payment at the door during delivery, however I suspect that they will make up their own charges, including currency conversion, despite HMRC using their own currency conversion methods to calculate VAT and duty due in the first instance.

Has anybody had any positive or negative experiences with deliveries? I can't determine which of the 3 carrier options to choose because their websites and phone helplines won't give me a cost estimate based on the price of an item, which is crazy. It looks to me like an easy way for them to load on charges to deliveries and hope the person signing for it is too stupid to understand they're being ripped off.

When I was in Canada we could tell the courier we would self declare customs clearance for items delivered from the USA, which would take all those stupid fees from $100 to $10. If you're buying a lot this saving soon adds up. Can we self clear with HMRC here and tell the courier companies to do one?