Same problem here in a manner of speaking.
Recieved a parcel from RHD Japan. Including postage the items cost me £430. However RHD only declared 38,000 yen approx which came in at around £172, this included the postage charge.
The parcel arrived on the Thursday, no problems there!!
On Sat I got a call from a female who said that she was from Fedex and that I owed £387 on duty!! I told her this was a mistake as this was (as far as she was concerned) double the value of the goods + postage. She became confused at my refusal to pay so I asked her if she could prove who she was as I would be unwilling to hand over card details to a stranger on the phone!!
She became even more confused and stated that she would need to send a letter or email, so I opted for the email.
The email confirmed she was from Fedex, but then a 1 week battle ensued where I asked for them to rectify their calculations, based on a conversion rate of 222.89 yen and VAT at 17.5%, followed by 3.5% duty and 2.5% Fedex admin. Eventaully a bill of £80 was agreed, although this was still in excess of 50% of the declared value + postage.
The issue was with customs, The goods +postage is used to calculate duty with a VAT conversion fee of £7.19. In addition to this because of the parcels size I was charged additional freight charges. These combined spiraled the costs up!!! Damn penny pinchers.
For ref I got my wife involved who is a Chartered ACCA and CTA accountant and Tax Advisor, she informed me that these later charges were well within HMRC's remit to impose.
Still even with duty I saved myself in excess of £300 on UK prices, a 2 row Greddy FMIC, Greddy diversion plate, cusco master cyclinder brace, greddy upper rad pipe and greddy oil cap for £430, not bad at all