Seems to be 2 separete issues here but I thought the OP's main problem was the fact that he thought he ordered from the UK, yet parts (whatever they were) came from the far east. I've been caught out with this before and is one reason, no matter how cheap, I won't buy from China on Ebay, and I won't use anyone who delivers through Hermes or Yodel.
I used to order lots of performance car parts from Japan, US and Australia for my Toyotas, it was always a complete lottery whether parts came through "clear" or whether they got held (there was no consistency then, presumably the same now). I've been charged nowt, vat, import duties, handling fees. Actually the only thing which actually *****d me off was RM charging me the cost of a stamp for sending the letter with charges! I mean, surely RM doesn't have to by a stamp to send a letter? You can't complain much otherwise if you know you're buying from outside the EU, but it would be better if there was consistency.
I'd be pretty miffed though if I'd paid for delivery from X and it came from Y with other charges. I know it's not uncommon now though (I can't remember the term for it). I orderd from someone in the UK on eBay last week, but goods came direct from Amazon -and I hate and avoid Amazon for many reasons (not that I find eBay too much better).
...The other thing is, when it's hapened to me before: I just don't accept deliveres from an unknown or unexpected company or courier, and perhaps I wouldn't pay any notice to a letter for import charges for something I ordered from the UK -if that was demonstrable. Might seem a bit harsh, but has made life a little bit easier on occasions before.