The only issue affecting you is that only people on your HH account can be MFU'd on your miles-- This has been around for a long time.

If you pay he should then be able to use his own miles to MFU.

here is link to T&C for MFU: http://www.britishairways.com/travel..._ae?sl=upgrade It doesnt say anything about who paid for the ticket....that I could see