Put it this way, if I got stopped on the way into the UK to pay VAT on this I think it would be obvious to the Customs agent what had happened and the retailer would be in deep water, not me!
Actually uncle
Smirn you may have unearthed something pretty serious here, clearly these staff are being trained to do this, perhaps you should go undercover and infiltrate them, then you could get to be on the 'telly