Dalby is now on numberplate recognition so you’d need to go beyond the barriers. If you head up the Dalby Drive towards Dixon’s hollow, keep going through the barriers as though leaving the forest.
You have a couple of options here, after around 200yds there’s a left turn onto a forest gravel road sign posted for Cross Cliff car park, it’s well out of the way and quiet plenty of space too, you can get on the red route here. Or alternately stay on the forest drive for another 1/2mile and you’ll find Bickley Gate carpark on the right, it’s right next to the forest drive but will be quiet enough, red route passes here too.
if you look on an ordnance survey map and follow the drive looking out for the names I’ve given you you’ll see where I mean.
Dont leave a mess and you’ll be fine on either site.
Enjoy