There are good, well used trails actually, its just that they are not that easy to find. Once you have them, they are pretty good (and steep – as in really steep). More flowing and floaty that really technical. Having said that, Marshal Law is much more technical.
Chelt Cycle Club have a section called The Corrective that maintain the trails as well as some other locals who build stuff there from time to time.
The overgrown trails will be old unused ones.
Best way is to be shown the top of the trails, but by yourself, Marshal Law is the easiest to find. From the smaller of the two Daisybank Road carparks, go straight up the big, wide, straight path to the flat bit by the old mine workings. Marshal Law starts on the right just where the track flattens. Its quite a steep slope straight off down to a tree where you do a sharp right turn. From there it is pretty obvious down to the big bomb hole by the bigger of the Daisybank car parks.
Mainline (which is the main section above Marshal Law from the top of the hill) is harder to find. Goto the trig point at the top, head on the west bound path. Stay on the main path, down the little limestone step down and turn left so that you re-enter the woods onto a wide path. The start area is at the top of the slight rise on the opposite side of the path you cross as you re-enter the woods. Its fairly obvious where to go once you start. Just be careful, there are a few steep bits that you can’t stop on once you start – good fun :).
You can do all of the tracks on a trail bike or hardcore hardtail and enjoy them fine. I do them on my On-One 456 quite often for a bit of a laugh. Marshal Law is best enjoyed with a decent bit of bounce at the back though 🙂