That's the car park I mentioned in my post last night. It wasn't an official car park but (from the security guy I talked to) they seemed ok with people going there as a lesser evil than parking along the narrow roads which were being used as access by the competitors.
@HKSjbg - I had a good old wander in Hafren last year and encountered a handful of other speccies, and none of the marshals or safety cars had any problem with me being there - though obviously I was in safe locations at all times.