I was in International Shipping but I can't remember exactly how it all works.
If you buy something in the UK with VAT, you claim the VAT back don't you?, then apply VAT when you sell in the UK.
If you buy within the EU, it would get messy - so by providing your VAT number to the seller, the seller can then export without accounting for VAT.
The "importer" - you - uses this method for deferred VAT payment.
i.e. you should declare your purchase within your VAT returns and pay the outstanding monies.