asinclai,
NPR = Noise Preferential Route.
Do you ever notice aircraft drifting close when on base leg for Redhill's 01? The controllers at Redhill sometimes mention it when I am in the circuit, not to me of course but others.
As a Gatwick approach atco, very occasionaly I've phoned Redhill ATC and asked them to watch traffic in their circuit getting a bit too far to the south. But it is so rare as not to be a problem.
Just a reminder as mentioned earlier in this thread that there's an instruction in the Terminal Control MATS (Manual of Air Traffic Services) Pt 2 which effectively precludes fixed wing VFR transits via the Gatwick overhead. So whether the atco's involved think such transits are a good idea or not, they are unable to offer them anyway.
WF.