Tax from UK to Gibraltar

Yes, you need to pay import duty on virtually everything into Gib.  Mostly at 12%, but occasionally at 6%.

BUT, and this is a big BUT, when ordering from the UK, (and this may apply to other countries, I have no idea) you should NOT be paying VAT. 

The company/ies you are dealing with should deduct the VAT from the total price, so that in effect, you end up with a cheaper product as the import duty is less than the VAT.

If the company you are dealing with does not do this, then go elsewhere.  I totally refuse to deal with companies who won't deduct the VAT.  Whatever rubbish excuse they give you is just garbage.  They have absolutely no legal right to charge you VAT if they are mailing/shipping something to Gibraltar as Gib is a VAT free zone.

Incidentally, the import duty is not related to the country of origin of the purchase, it is exactly what it says, an import duty.  Up to you to do battle with the suppliers you are buying from.

Hope that helps, if there is anything you don't understand, please ask again.