The regulator is Safety Regulation Group (SRG) which is a branch of the CAA based at Gatwick. Part of the selling point of PPP was that SRG would then become an independent regulator (rather than part of the same umbrella organisation as NATS) and therefore have more teeth.
I am not deeply involved in the process, but as far as I am aware, SRG has NEVER blocked anything involved in the operation or opening of NERC and is generally seen to be very proficient in the use of the rubber stamp. Indeed, a QC who was engaged to give an opinion on the legality of operating with the display problems we had felt it was an odd arrangement. He thought (as most people would) that a regulator should satisfy itself that the system is correct and that process should involve the inspection of facilities and questioning of procedures. In effect, NATS should PROVE that the system is correct. The NATS/SRG relationship seems to be one where NATS says it is OK and SRG has to prove otherwise!
Good, eh!?