Having had a PCS briefing, I can tell you.
PCS do not want seperate bargaining. The question was asked very quickly and the answer in a nutshell was, there's little we can do about it... NATS hold the purse strings and so - to an extent - hold the power to decide who they talk to about what.
There's only one of the 3 TU branches that benefits from splitting - and I don't believe they engineered it either. From day one this has looked to me like a new management team attempting to lay a new set of rules for future years.