In/on a vehicle - no on closed roads you can't access the campsite. You can get under Quarterbridge on foot with with some careful adventure(be prepared to get wet feet) . Going under Braddan Bridge on the Access Road either on foot or vehicle will get you to the inside of the course and I think from Braddan Road where the roads closed rope goes across you can jump up behind the wall and then trek through the trees to the campsite - this might not be the case now as I haven't been through there for a few years. I used to muck around down there as a kid it might be worth a look to see if there's a legal route at the top end of the campsite leading on foot to the Tromode Road which in turn will get you to the bottom of Bray Hill, probably worth an open roads recce on arrival .. have a good time.