Someone I know (not me
) saved money on his mortgage by having his bank account (savings and mortgage, higher the savings, the lower the mortgate interest) be same account as where all of his provate company money was stored. This built up quite a nice amount of money, saving him a lot of money on his mortgage. He contacted hmrc and said that as he was not recieving any income, they couldn't tax him on it.
So I would think (hope) the same applies to air miles.
Paul