Brandon Country Park car park as mentioned…..
If you are planning on doing the waymarked trails, then head back up from the car park to the main road. Cross the road, back into the forest and almost immediately there is a non-signposted trail on the right hand side.
Follow it down. It splits a few times, but doesn’t matter what path you take as long as you are generally heading in the same direction. You’ll end up at a fire road at the bottom of The Beast.
From here you can either follow the signs (on your left, turn left back into the forest) to do the last bit of the trail.
Or, to get to the start of the trails go left up the fire road and when it bears round to the right after a few hundred yards, continue straight up on a grass/sand track (instead of following it right).
At the end of this, turn right onto the sandy path. Follow this until the end of a grassy field on you right and go left onto a gravel road. This takes you to the start of the waymarked trails.