I do occasionally read the forum lol. We parked in the free car park for Plas Newydd. You can see the dolmen from the car park itself. Instead of going into the visitor centre building, I just walked over to the gate (which leads onto the road down to the house), ducked through the fence and walked over to it. No one said anything. I spent a good while there then walked back the same way. There were people all over, no one seemed bothered.