Two other options to consider....

Emirates should run at about £1500 and you can get BA miles (but not tier points) for this.

Max out on the AY ticket by ticketing via BKK on both legs - many fares offer a free stopover, so you'd end up with 40+120+40 each way. I can't however comment on the logistics of convincing someone to ticket this without waiting 24hrs for the next flight as the connection is possibly illegal.....