Make sure that a copy of the original receipt showing that VAT was paid at the time of purchase is included in the documentation with the shipment of the computer. Although an item that is VAT paid in one EU country is deemed to be VAT paid in all of them, customs officials in the destination country may still want to see evidence that VAT was paid at the time of purchase. It follows of course that you cannot also reclaim the VAT when you export the computer from the UK.