Something that you might find interesting happened to me the other day. I was offered a Poug at the Mmb for a flight from Lgw to Lca (£89) and when I tried to get it I got an error message saying there is a problem upgrading this flight. Tried a few more times during the next couple of days but the same thing happened, so I phoned BA and they gave me the same Poug over the phone. At no extra cost. The standard upgrade at the time was in excess of £300.