Products purchased inside of UK territory, which then are exported outside of UK borders. Must show a valid purchase order with relevant EU or other importation documentation, specific to country equipment will be advanced onto.
This is a HMRC requirement under VAT notice 703 relating to goods entering europe from UK mainland.
Therefore failure to produce the correct documentation will result in items being sold with VAT added @ 20% UK rate.
If documentation is not available, then the notice 703 on HMRC website states vat has to be added onto goods purchased within the UK mainland.
For more information on VAT chargeable inside and outside of UK borders talk to Solar Dragons