Ray - LGW (and previously the regions) had their own local councils who dealt with local issues such as rostering whilst larger issues like pay were dealt with on a central level. The relations between the different local groups are tied up pretty tightly with strict controls on where each group can operate, primarily to stop BA running down the best paid group and ramping up a lower paid group in order to do their work. The system was not entirely without tension, but to my mind worked better than having a free-for-all with everyone trying to undercut each other. Whilst you might occasionally be peeved by something, everyone knew they had their chance at the big shot at LHR and didn't want to destroy that. I would predict that an OS CC would work in a similar way. Their geographical area of operation would be fixed (as is Gatwicks) and the OS CC would deal with their own domestic issues. I don't know how pay would work but I'd hazard a guess the current system with the BACC negotiating centrally would be more beneficial than BA's planned system of having us all undercut each other.
Nobody every said it would be simple!