As highlighted on a recent thread on P.F, the U.K supplier should have deducted the U.K VAT as it's now a sale for export.
That supplier could, if set up for it, have dealt with the VAT due in the O.Ps country thus avoiding any collection charges there.

The O.P needs to check the paperwork with the items, it may be that VAT has been sorted out and it's the receiving Customs unit that's got it wrong in trying to charge.