BMI has been active in advertising in the Economist. Also, there was the "BMI Time" adverts on TV, which I thought excellent.
You have to remember that BA and BMI are trying to attract the mass market to major destinations. A large part of BMI's business is to niche markets, such as Freetown, Khartoum, Almaty, Aleppo etc...mainstream advertising in the mass media for these markets would be money ill spent, and specific marketing aimed at businesses and communities with known links to these destinations would be far more prudent.