Wharny is pretty far removed from a trail centre, it's all a bit less organised (which I personally like). Very rooty, rocky, off camber and tricky in places so a 6 inch travel bike won't be wasted (it's what I ride).
It turns into a quagmire quite quickly so it helps if you're okay with mud. Also at the moment a couple of sections of trail have fallen victim to the forestry work, and a lot is overgrown with bracken.
It's not that easy to find all the good stuff without local assistance but there are lots of good trails, particularly DH stuff. Steve Peat learnt his trade in them there woods.
Our regular XC route seems to take about an hour and half or so, taking in a few DH sections.
As for parking, to be honest I think it's better to park outside the Pheasant pub in Oughtibridge for the simple reason that you finish the ride with a big cruise downhill rather than a long slog of a climb 🙂