NSL isn't making enough to fund a pay rise because it selling its services too cheaply.
NSL provides an excellent service and it shouldn't be afraid to charge for that excellence.
The airports are tightly integrated with TC & NERL systems. This tight integration is made possible because NSL & NERL are part of the same group.
If BAA or GIP think they could get the same through put of aircraft by employing someone like SERCO to do their ATC they'd be in for a very big surprise.