There are a couple of threads along this line on here. One I started is this one.
Where things are marked black at Lee they are usually pretty hard, compared to black marked sections elsewhere. I go to Lee and Cragg quite a bit now, they are only 20 minutes away from my house, and just ride the main red sections. The signposting is censored , but part of this is because areas are designed for riding repeatedly you can end up unintentionally looping round by following red markers. After a couple of visits you'll find the way.
I have a had a couple of hairy moments where I've lost momentum on the final descent at Lee and got a bit stuck in the rocks, but this hasn't happened for a while. The rest of the red is all OK, just weigh up the sections in advance, although the first rocky slab uphill section and some of the short climbs are just an impossibility to me at the moment. This is both a skill and fitness issue.
Cragg is much more of the type of trail you'd expect at other trail centres, and I really enjoy it. My current preference is to do the first half of Lee, then over the moors to Cragg, a lap of Cragg then it is basically all downhill to do the last downhill section of Lee then back to the car park. It's best to go there with someone though, especially during the week, as it can be really quiet.