As far as I can tell. Your friend would not get a refund because he lives in the UK.
In order to get a VAT refund, you would have to come to the UK buy the products yourself, fill in a form and then get the refund when you leave the country. You would also need to transport products with you on the plane.
http://www.visitbritain.com/VB3-en-A...t_refunds.aspx
http://customs.hmrc.gov.uk/channelsP...CE_PROD_007779
http://customs.hmrc.gov.uk/channelsP...HMCE_CL_001454
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