In reply to Paul Evans:
Thanks Paul.
As it happens, when I arrived I saw the little car park was open and other cars using it. Couldn't see any signs saying it was private or not allowed so parked there (where I have parked for years) presuming it was still ok.
At around 3pm, a kind random chap, ran in to the quarry and told all climbers present that the land owner locks the gate between 3:30 and 4pm.
We ran back to the cars for 3:25 to find the gates being locked already. Close call.
I spoke to to the bloke who was locking up and asked if parking was permitted at all and he said no. He said "it's private land and nobody can park here" claiming the police dished out tickets to cars using it recently.
I did (diplomatically) point out that there was no signage making it clear but he says there is(??).
Anyway, I made my apologies and he seemed ok (let us out anyway), but he must have locked at least 6 in behind us.
Needless to say it was a close call. I would say avoid the car park, use the lane or visitors center.