Having done a bit of searching, it's not clear how BA's wines are selected. A few places name Andy Sparrow (and he's in a BA YouTube video talking about wine selection), but he works for Bibendum.
There was an overview article from Decanter outlining the scale of airline purchases -
https://www.decanter.com/features/ai...t-life-372891/
Google also returned an interesting PDF on the Masters of Wine site (apparently confidential) - almost a tender document for consultants to be part of the process in 2019/20 -
https://www.mastersofwine.org/downlo...AE3EBDA3AE49BD - there's also an html version here -
https://webcache.googleusercontent.c...&ct=clnk&gl=uk