AVA, it must be great only having to work part time, facilitated by living in what is one of the cheapest major cities in the world whilst earning a wage in a very high cost economy. On top of this, you only have to turn up in London once a month on a discounted ticket.
Sorry to say it, but I don't feel sorry for you.
There could be tax liabilities if BA are seen to subsidise or make easier commuting to work. Could commuting be seen as a benefit in kind like benefiting from a company car?