Seeing as Glenn is being a total slacko and not looking at the board right now, I'll attempt to answer on his behalf.
I believe they parked elsewhere (not sure where...I didn't speak to them) and walked from Gen Holmes Dr (southern side) up the hill and to the fenceline where Matthew then saw them.
Security did have a friendly chat to them (2 separate security patrols), it was smiles all round because everyone was polite and friendly, and they continued spotting there until a rain shower and some pretty crappy dark photo-unfriendly cloud came in from the south east.
I was going to stop and say hi, but they'd gone by the time I returned to that area. I didn't see where they went.
As far as I know, at no time did they wander through the construction compound area there near gate 16. All access was via the hill next to GHD.
Glenn, feel free to add to or correct me here...
Cheers
Nigel