There is something involving 50%, Avios, BA and Black Friday, but it's not a discount, it's a bonus. And, unfortunately for the OP, it doesn't involve booking a seat on a flight.

If you use the BA estore you get an extra 50% Avios (and that's on top of any special promotions, such as 8 instead of 4 Avios per pound at a certain merchant) all the way up to Christmas.