Most airport operators are only interested in the bottom line. That is why using airports is almost always a painful experience.
In terms of ATC, aren't we right to believe that all ATC personnel CAA licensed whether NATS or otherwise are all of the same or at least comparable ability and competence.
So really whoever the ATC provider is at BHX and LGW their level of service is the same, but the price they offer their services at is different.
To say otherwise is to open a can of worms is it not?