If that had been the case, then BA could have kept the regional bases. It doesnt work like that. LHR has high yeilds gatwick and the regions dont. therefore the costs must be lower. Its not like the RJ100's or the ERJ's are as comfortable as a A319, but the market cant take the 319's costs, just as it cant take Mainlines costs (and i'm not supporting them at all)
Ref Cabin Crew loyalty, BA doesnt have loyalty it has Cabin Crew who wont move because they wont get the money elsewhere which is not a good situation, and in my experience the BACX CCrew in the regions are much better at Full service than the BA ones because they know the world doesnt owe them a living.