What domination ? Every time I go to Heathrow I see a huge range of carriers operating besides BA/BMI. It's nothing like going to Dallas, or Seoul, or similar, and seeing 90% by one carrier. You can see the same in the UK, at Southampton (FlyBe), even Stansted is heading that way with Ryanair. Nobody has complained about domination there.
When BA withdrew from the regions it wasn't through some fit of pique, it was because a huge range of competitive options from European and Intercontinental airlines had made services from there no longer worthwhile. Some domination !
BA and BMI used to be the key two operators on London to Scotland; now it's BA and Easyjet, which latter have taken the bulk of the leisure market. It really doesn't sustain a limitless number of operators.