HM Revenue and Customs (HMRC) does not hold information on VAT to this level of detail. The Retail Export scheme is operated and administered by the participating retailers. Retailers do not separately identify retail exports on their VAT returns so HMRC does not hold any record of the actual VAT refunds made.
In a 2013 consultation document VAT: Retail Export Scheme, HMRC estimated that, in the UK, more than £300 million of VAT is refunded under the VAT Retail Export Scheme each year. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/209487/20130627_Consultation_document_1_0_complete.pdf (Paragraph 2.4)