Well, I speak as one who found a low fare from Go, albeit with a Daily Telegraph offer soon after the 11th Sept I paid £30 Bristol-Glasgow return. Unfortunately I never made the flight so cannot report on the service (articulated lorry on a wet road, one very squashed Escort, one slightly squashed me).
Go is now an independent company, so competitors cannot complain about its protection by BA as they used to. BMI are at liberty to make their views known, as is anyone else, to the CAA as pointed out in a previous post. If Go had an unwarranted advantage, either from EMA or the regulators that was not available to BMI then BMI they have a legitimate complaint, presumably addressed by someone at the department of trade and industry, in competition regulation. Otherwise, if they just miss the boat, then they will have to put up. I assume regulators will tell them so.
As a final point, when I finally went up to GLA the cheapest way was BA from LHR - £65 rtn, but I cheated a little and got my friend a BA pilot to buy the ticket. The flight was great, fairly empty, and they had London Pride to drink. More than once BA has been the cheapest. Sometimes it is Easy or Go. Shop around, people, like good little consumers. It is what should make capitalism work. Modern advertising is an attempt to subvert capitalism!