And to prove Heathrow Director's statement, following an MOR a few months ago (I think by one of the London sectors), the BMI Baby from Paris to Durham Tees Valley has been "renamed" BMI56K, however the outbound causes no confusion and remains the same as the passenger flight number (which I cannot remember right now - BMI4977?)
Of course the potential "danger" still exists if BA decide to have BAW14AL and Midland decide to have BMI14AL...then you're back to square one :-)
-HD-