I complained too, the seller has refunded me £10 and I'm OK with that.I have complained and seller has asked to see the slip. I am sure Amazon has it covered in the Ts and Cs but I will see what I can do
When I went online to pay the Royal Mail I noticed that the charge is £4.12 Customs, £8.00 Royal Mail handling 😯
I've bought a few parts for my Brommie off Ebay sellers, including a Titanium seat post and never been hit with fees before.
Maybe it's an Amazon thing.